more work on bundler tests (#2667)

* Fix `make dev` reusing old .o file

* more bundler tests

* document capture

* bundler tests

* bundler tests

* bundler tests

* finish up

* remove bad thing to merge on main

18 files changed, 826 insertions, 215 deletions

diff --git a/Makefile b/Makefile
index d2d577460..05deffc10 100644
--- a/Makefile
+++ b/Makefile
@@ -1084,7 +1084,7 @@ dev-obj-linux:
 dev: mkdir-dev dev-obj bun-link-lld-debug
 
 mkdir-dev:
-	mkdir -p $(DEBUG_PACKAGE_DIR)/bin
+	mkdir -p $(DEBUG_PACKAGE_DIR)
 
 test-all:
 	$(RELEASE_BUN) test
diff --git a/test/bundler/bundler_cjs2esm.test.ts b/test/bundler/bundler_cjs2esm.test.ts
index 4c37e9591..ffe9a98f8 100644
--- a/test/bundler/bundler_cjs2esm.test.ts
+++ b/test/bundler/bundler_cjs2esm.test.ts
@@ -4,5 +4,23 @@ import { bundlerTest, expectBundled, itBundled, testForFile } from "./expectBund
 var { describe, test, expect } = testForFile(import.meta.path);
 
 describe("bundler", () => {
-  return;
+  // TODO: I must be misunderstanding how the cjs to esm transforms work. since this should pass
+  itBundled("cjs2esm/ModuleExportsFunction", {
+    files: {
+      "/entry.js": /* js */ `
+        import { foo } from 'lib';
+        console.log(foo());
+      `,
+      "/node_modules/lib/index.js": /* js */ `
+        module.exports.foo = function() {
+          return 'foo';
+        }
+      `,
+    },
+    minifySyntax: true,
+    platform: "bun",
+    onAfterBundle(api) {
+      assert(!api.readFile("/out.js").includes("__commonJS"), "should not include the commonJS helper");
+    },
+  });
 });
diff --git a/test/bundler/bundler_edgecase.test.ts b/test/bundler/bundler_edgecase.test.ts
index cb8a90b81..98c8c0a8e 100644
--- a/test/bundler/bundler_edgecase.test.ts
+++ b/test/bundler/bundler_edgecase.test.ts
@@ -37,18 +37,50 @@ describe("bundler", () => {
     },
     run: true,
   });
-  // itBundled("edgecase/PureCommentInLineComment", {
-  //   files: {
-  //     "/entry.js": /* js */ `
-  //       (function () {
-  //         // Some text that contains a pure comment in it like /* @__PURE__ */, with other text around it.
+  itBundled("edgecase/BunPluginTreeShakeImport", {
+    // This only appears at runtime and not with bun build, even with --transform
+    files: {
+      "/entry.ts": /* js */ `
+        import { A, B } from "./somewhere-else";
+        import { plugin } from "bun";
 
-  //         // console.log;
+        plugin(B());
 
-  //         fn2("TODO: should this call be kept?");
-  //       })();
-  //     `,
-  //   },
-  //   dce: true,
-  // });
+        new A().chainedMethods();
+      `,
+      "/somewhere-else.ts": /* js */ `
+        export class A {
+          chainedMethods() {
+            console.log("hey");
+          }
+        }
+        export function B() {
+          return { name: 'hey' }
+        }
+      `,
+    },
+    external: ["external"],
+    mode: "transform",
+    minifySyntax: true,
+    platform: "bun",
+    run: { file: "/entry.ts" },
+  });
+  itBundled("edgecase/TemplateStringIssue622", {
+    files: {
+      "/entry.ts": /* js */ `
+        capture(\`\\?\`);
+        capture(hello\`\\?\`);
+      `,
+    },
+    capture: ["`\\\\?`", "hello`\\\\?`"],
+    platform: "bun",
+  });
+  itBundled("edgecase/StringNullBytes", {
+    files: {
+      "/entry.ts": /* js */ `
+        capture("Hello\0");
+      `,
+    },
+    capture: ['"Hello\0"'],
+  });
 });
diff --git a/test/bundler/bundler_minify.test.ts b/test/bundler/bundler_minify.test.ts
new file mode 100644
index 000000000..7eacfbde6
--- /dev/null
+++ b/test/bundler/bundler_minify.test.ts
@@ -0,0 +1,54 @@
+import { describe } from "bun:test";
+import { itBundled } from "./expectBundled";
+
+describe("bundler", () => {
+  itBundled("minify/TemplateStringFolding", {
+    files: {
+      "/entry.js": /* js */ `
+        capture(\`\${1}-\${2}-\${3}-\${null}-\${undefined}-\${true}-\${false}\`);
+        capture(\`\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C\`.length)
+        capture(\`\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C\`.length === 8)
+        capture(\`\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C\`.length == 8)
+        capture(\`\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C\`.length === 1)
+        capture(\`\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C\`.length == 1)
+        capture("\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C".length)
+        capture("\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C".length === 8)
+        capture("\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C".length == 8)
+        capture("\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C".length === 1)
+        capture("\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C".length == 1)
+        capture('\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C'.length)
+        capture('\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C'.length === 8)
+        capture('\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C'.length == 8)
+        capture('\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C'.length === 1)
+        capture('\\uD83D\\uDE0B \\uD83D\\uDCCB \\uD83D\\uDC4C'.length == 1)
+        capture(\`😋📋👌\`.length === 6)
+        capture(\`😋📋👌\`.length == 6)
+        capture(\`😋📋👌\`.length === 2)
+        capture(\`😋📋👌\`.length == 2)
+      `,
+    },
+    capture: [
+      '"1-2-3-null-undefined-true-false"',
+      "8",
+      "true",
+      "true",
+      "false",
+      "false",
+      "8",
+      "true",
+      "true",
+      "false",
+      "false",
+      "8",
+      "true",
+      "true",
+      "false",
+      "false",
+      "true",
+      "true",
+      "false",
+      "false",
+    ],
+    platform: "bun",
+  });
+});
diff --git a/test/bundler/esbuild/css.test.ts b/test/bundler/esbuild/css.test.ts
index 2e0798082..83203cb6c 100644
--- a/test/bundler/esbuild/css.test.ts
+++ b/test/bundler/esbuild/css.test.ts
@@ -350,7 +350,7 @@ var { describe, test, expect } = testForFile(import.meta.path);
 //     /* TODO FIX expectedScanLog: `entry.css: ERROR: Bundling with conditional "@import" rules is not currently supported
 //   `, */
 //   });
-//   itBundled("css/CSSAndJavaScriptCodeSplittingIssue1064", {
+//   itBundled("css/CSSAndJavaScriptCodeSplittingESBuildIssue1064", {
 //     // GENERATED
 //     files: {
 //       "/a.js": /* js */ `
@@ -376,7 +376,7 @@ var { describe, test, expect } = testForFile(import.meta.path);
 //     format: "esm",
 //     splitting: true,
 //   });
-//   itBundled("css/CSSExternalQueryAndHashNoMatchIssue1822", {
+//   itBundled("css/CSSExternalQueryAndHashNoMatchESBuildIssue1822", {
 //     // GENERATED
 //     files: {
 //       "/entry.css": /* css */ `
@@ -391,7 +391,7 @@ var { describe, test, expect } = testForFile(import.meta.path);
 //   NOTE: You can mark the path "foo/bar.png#baz" as external to exclude it from the bundle, which will remove this error.
 //   `, */
 //   });
-//   itBundled("css/CSSExternalQueryAndHashMatchIssue1822", {
+//   itBundled("css/CSSExternalQueryAndHashMatchESBuildIssue1822", {
 //     // GENERATED
 //     files: {
 //       "/entry.css": /* css */ `
diff --git a/test/bundler/esbuild/dce.test.ts b/test/bundler/esbuild/dce.test.ts
index 8b3e2c289..4ba4f4b48 100644
--- a/test/bundler/esbuild/dce.test.ts
+++ b/test/bundler/esbuild/dce.test.ts
@@ -641,7 +641,7 @@ describe("bundler", () => {
       stdout: "1",
     },
   });
-  itBundled("dce/PackageJsonSideEffectsFalseNoWarningInNodeModulesIssue999", {
+  itBundled("dce/PackageJsonSideEffectsFalseNoWarningInNodeModulesESBuildIssue999", {
     files: {
       "/Users/user/project/src/entry.js": /* js */ `
         import "demo-pkg"
diff --git a/test/bundler/esbuild/default.test.ts b/test/bundler/esbuild/default.test.ts
index 93bc21492..5ee1c0f1c 100644
--- a/test/bundler/esbuild/default.test.ts
+++ b/test/bundler/esbuild/default.test.ts
@@ -1,6 +1,13 @@
 import assert from "assert";
 import dedent from "dedent";
-import { ESBUILD_PATH, bundlerTest, expectBundled, itBundled, testForFile } from "../expectBundled";
+import {
+  ESBUILD_PATH,
+  RUN_UNCHECKED_TESTS,
+  bundlerTest,
+  expectBundled,
+  itBundled,
+  testForFile,
+} from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -1012,27 +1019,39 @@ describe("bundler", () => {
       stdout: "./test.txt",
     },
   });
-  itBundled("default/RequireWithoutCall", {
-    // TODO: MANUAL CHECK: `require` on line one has to be renamed to `__require`
+  itBundled("default/RequireWithoutCallPlatformNeutral", {
+    // `require` on line one has to be renamed to `__require`
     files: {
       "/entry.js": /* js */ `
         const req = require
         req('./entry')
+        capture(req)
       `,
     },
     platform: "neutral",
+    onAfterBundle(api) {
+      const varName = api.captureFile("/out.js")[0];
+      const assignmentValue = api.readFile("/out.js").match(new RegExp(`${varName} = (.*);`))![1];
+      expect(assignmentValue).not.toBe("require");
+    },
   });
-  itBundled("default/NestedRequireWithoutCall", {
-    // TODO: MANUAL CHECK: `require` on line one has to be renamed to `__require`
+  itBundled("default/NestedRequireWithoutCallPlatformNeutral", {
+    // `require` on line one has to be renamed to `__require`
     files: {
       "/entry.js": /* js */ `
         (() => {
           const req = require
           req('./entry')
+          capture(req)
         })()
       `,
     },
     platform: "neutral",
+    onAfterBundle(api) {
+      const varName = api.captureFile("/out.js")[0];
+      const assignmentValue = api.readFile("/out.js").match(new RegExp(`${varName} = (.*);`))![1];
+      expect(assignmentValue).not.toBe("require");
+    },
   });
   itBundled("default/RequireWithCallInsideTry", {
     files: {
@@ -1067,7 +1086,7 @@ describe("bundler", () => {
     run: [{ file: "/test1.js" }, { file: "/test2.js" }],
   });
   itBundled("default/RequireWithoutCallInsideTry", {
-    // TODO: MANUAL CHECK: `require` on line one has to be renamed to `__require`
+    // `require` has to be renamed to `__require`
     files: {
       "/entry.js": /* js */ `
         try {
@@ -1075,10 +1094,16 @@ describe("bundler", () => {
           var aliasedRequire = require;
           aliasedRequire('./locale/' + name);
           getSetGlobalLocale(oldLocale);
+          capture(aliasedRequire)
         } catch (e) {}
       `,
     },
     platform: "neutral",
+    onAfterBundle(api) {
+      const varName = api.captureFile("/out.js")[0];
+      const assignmentValue = api.readFile("/out.js").match(new RegExp(`${varName} = (.*);`))![1];
+      expect(assignmentValue).not.toBe("require");
+    },
   });
   itBundled("default/RequirePropertyAccessCommonJS", {
     files: {
@@ -1886,10 +1911,6 @@ describe("bundler", () => {
     outfile: "/out.js",
     minifyIdentifiers: true,
     mode: "transform",
-    run: {
-      // TODO: use bun here after https://github.com/oven-sh/bun/issues/1724 is fixed
-      runtime: "node",
-    },
   });
   itBundled("default/WithStatementTaintingNoBundle", {
     // TODO: MANUAL CHECK: make sure the snapshot we use works.
@@ -1977,7 +1998,7 @@ describe("bundler", () => {
       assert(!text.includes("renameMe"), "Should have renamed all `renameMe` variabled");
     },
   });
-  itBundled("default/ImportReExportES6Issue149", {
+  itBundled("default/ImportReExportES6ESBuildIssue149", {
     files: {
       "/app.jsx": /* jsx */ `
         import { p as Part, h, render } from './import';
@@ -2405,7 +2426,7 @@ describe("bundler", () => {
       stdout: '[{},{},{"foo":123},{"bar":123}] true',
     },
   });
-  itBundled("default/EmptyExportClauseBundleAsCommonJSIssue910", {
+  itBundled("default/EmptyExportClauseBundleAsCommonJSESBuildIssue910", {
     files: {
       "/entry.js": `console.log(JSON.stringify(require('./types.mjs')))`,
       "/types.mjs": `export {}`,
@@ -2432,7 +2453,7 @@ describe("bundler", () => {
       assert(api.readFile("/out.js").includes('"use strict";'), '"use strict"; was emitted');
     },
   });
-  itBundled("default/UseStrictDirectiveBundleIssue1837", {
+  itBundled("default/UseStrictDirectiveBundleESBuildIssue1837", {
     files: {
       "/entry.js": /* js */ `
         const p = require('./cjs').foo;
@@ -2453,7 +2474,7 @@ describe("bundler", () => {
       stdout: "function",
     },
   });
-  itBundled("default/UseStrictDirectiveBundleIIFEIssue2264", {
+  itBundled("default/UseStrictDirectiveBundleIIFEESBuildIssue2264", {
     files: {
       "/entry.js": /* js */ `
         'use strict'
@@ -2465,7 +2486,7 @@ describe("bundler", () => {
       assert(api.readFile("/out.js").includes('"use strict";'), '"use strict"; should be emitted');
     },
   });
-  itBundled("default/UseStrictDirectiveBundleCJSIssue2264", {
+  itBundled("default/UseStrictDirectiveBundleCJSESBuildIssue2264", {
     files: {
       "/entry.js": /* js */ `
         'use strict'
@@ -2477,7 +2498,7 @@ describe("bundler", () => {
       assert(api.readFile("/out.js").includes('"use strict";'), '"use strict"; should be emitted');
     },
   });
-  itBundled("default/UseStrictDirectiveBundleESMIssue2264", {
+  itBundled("default/UseStrictDirectiveBundleESMESBuildIssue2264", {
     files: {
       "/entry.js": /* js */ `
         'use strict'
@@ -4222,7 +4243,7 @@ describe("bundler", () => {
       stdout: `[[1,1,1],[1,1,1],[2,2,2,null,null]]`,
     },
   });
-  itBundled("default/DefineInfiniteLoopIssue2407", {
+  itBundled("default/DefineInfiniteLoopESBuildIssue2407", {
     files: {
       "/entry.js": /* js */ `
         a.b()
@@ -4568,7 +4589,7 @@ describe("bundler", () => {
   //   mode: "transform",
   //   external: ["a", "b", "c", "react/jsx-dev-runtime"],
   // });
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   // I cant get bun to use `this` as the JSX runtime. It's a pretty silly idea anyways.
   itBundled("default/JSXThisValueCommonJS", {
     files: {
@@ -4999,7 +5020,7 @@ describe("bundler", () => {
     },
     external: ["some-path"],
   });
-  itBundled("default/StrictModeNestedFnDeclKeepNamesVariableInliningIssue1552", {
+  itBundled("default/StrictModeNestedFnDeclKeepNamesVariableInliningESBuildIssue1552", {
     // GENERATED
     files: {
       "/entry.js": /* js */ `
@@ -5784,7 +5805,7 @@ describe("bundler", () => {
   b.js: NOTE: Another definition of "x" comes from "b.js" here:
   `, */
   });
-  itBundled("default/NonDeterminismIssue2537", {
+  itBundled("default/NonDeterminismESBuildIssue2537", {
     // GENERATED
     files: {
       "/entry.ts": /* ts */ `
@@ -6327,7 +6348,7 @@ describe("bundler", () => {
       `,
     },
   });
-  itBundled("default/ErrorMessageCrashStdinIssue2913", {
+  itBundled("default/ErrorMessageCrashStdinESBuildIssue2913", {
     // GENERATED
     files: {
       "/project/node_modules/fflate/package.json": `{ "main": "main.js" }`,
diff --git a/test/bundler/esbuild/importstar.test.ts b/test/bundler/esbuild/importstar.test.ts
index 482655236..c9b78f7be 100644
--- a/test/bundler/esbuild/importstar.test.ts
+++ b/test/bundler/esbuild/importstar.test.ts
@@ -1028,7 +1028,7 @@ describe("bundler", () => {
       stdout: '{"foo":"foo"}',
     },
   });
-  itBundled("importstar/Issue176", {
+  itBundled("importstar/ESBuildIssue176", {
     files: {
       "/entry.js": /* js */ `
         import * as things from './folders'
@@ -1102,7 +1102,7 @@ describe("bundler", () => {
       stdout: '{"bar":"bar","foo":"foo"}',
     },
   });
-  itBundled("importstar/ImportDefaultNamespaceComboIssue446", {
+  itBundled("importstar/ImportDefaultNamespaceComboESBuildIssue446", {
     files: {
       "/external-default2.js": /* js */ `
         import def, {default as default2} from 'external'
diff --git a/test/bundler/esbuild/importstar_ts.test.ts b/test/bundler/esbuild/importstar_ts.test.ts
index 5641753c0..76afe6d7e 100644
--- a/test/bundler/esbuild/importstar_ts.test.ts
+++ b/test/bundler/esbuild/importstar_ts.test.ts
@@ -1,5 +1,5 @@
 import { test, describe } from "bun:test";
-import { expectBundled, itBundled } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, expectBundled, itBundled } from "../expectBundled";
 
 // Tests ported from:
 // https://github.com/evanw/esbuild/blob/main/internal/bundler_tests/bundler_importstar_ts_test.go
@@ -7,7 +7,7 @@ import { expectBundled, itBundled } from "../expectBundled";
 // For debug, all files are written to $TEMP/bun-bundle-tests/ts
 
 describe("bundler", () => {
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("ts/TSImportStarUnused", {
     // GENERATED
     files: {
diff --git a/test/bundler/esbuild/loader.test.ts b/test/bundler/esbuild/loader.test.ts
index 648464d6e..1ca741749 100644
--- a/test/bundler/esbuild/loader.test.ts
+++ b/test/bundler/esbuild/loader.test.ts
@@ -1,4 +1,4 @@
-import { expectBundled, itBundled, testForFile } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, expectBundled, itBundled, testForFile } from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -31,7 +31,7 @@ describe("bundler", () => {
     },
   });
 
-  itBundled("loader/LoaderJSONSharedWithMultipleEntriesIssue413", {
+  itBundled("loader/LoaderJSONSharedWithMultipleEntriesESBuildIssue413", {
     // GENERATED
     files: {
       "/a.js": /* js */ `
@@ -62,8 +62,7 @@ describe("bundler", () => {
       },
     ],
   });
-
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("loader/LoaderFile", {
     // GENERATED
     files: {
diff --git a/test/bundler/esbuild/lower.test.ts b/test/bundler/esbuild/lower.test.ts
index b22cdbd74..23b18397d 100644
--- a/test/bundler/esbuild/lower.test.ts
+++ b/test/bundler/esbuild/lower.test.ts
@@ -1,4 +1,4 @@
-import { expectBundled, itBundled, testForFile } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, expectBundled, itBundled, testForFile } from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -7,7 +7,7 @@ var { describe, test, expect } = testForFile(import.meta.path);
 // For debug, all files are written to $TEMP/bun-bundle-tests/lower
 
 describe("bundler", () => {
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("lower/LowerOptionalCatchNameCollisionNoBundle", {
     // GENERATED
     files: {
@@ -1207,7 +1207,7 @@ describe("bundler", () => {
     },
     unsupportedJSFeatures: "es2021",
   });
-  itBundled("lower/LowerPrivateSuperStaticBundleIssue2158", {
+  itBundled("lower/LowerPrivateSuperStaticBundleESBuildIssue2158", {
     // GENERATED
     files: {
       "/entry.js": /* js */ `
@@ -1451,7 +1451,7 @@ describe("bundler", () => {
     unsupportedJSFeatures: "es2018",
     mode: "transform",
   });
-  itBundled("lower/ClassSuperThisIssue242NoBundle", {
+  itBundled("lower/ClassSuperThisESBuildIssue242NoBundle", {
     // GENERATED
     files: {
       "/entry.ts": /* ts */ `
@@ -1678,7 +1678,7 @@ describe("bundler", () => {
     },
     mode: "passthrough",
   });
-  itBundled("lower/LowerPrivateClassFieldStaticIssue1424", {
+  itBundled("lower/LowerPrivateClassFieldStaticESBuildIssue1424", {
     // GENERATED
     files: {
       "/entry.js": /* js */ `
@@ -1692,7 +1692,7 @@ describe("bundler", () => {
       `,
     },
   });
-  itBundled("lower/LowerNullishCoalescingAssignmentIssue1493", {
+  itBundled("lower/LowerNullishCoalescingAssignmentESBuildIssue1493", {
     // GENERATED
     files: {
       "/entry.js": /* js */ `
diff --git a/test/bundler/esbuild/packagejson.test.ts b/test/bundler/esbuild/packagejson.test.ts
index 0cdb46569..e3e5387b3 100644
--- a/test/bundler/esbuild/packagejson.test.ts
+++ b/test/bundler/esbuild/packagejson.test.ts
@@ -1,4 +1,4 @@
-import { expectBundled, itBundled, testForFile } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, expectBundled, itBundled, testForFile } from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -7,7 +7,7 @@ var { describe, test, expect } = testForFile(import.meta.path);
 // For debug, all files are written to $TEMP/bun-bundle-tests/packagejson
 
 describe("bundler", () => {
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("packagejson/PackageJsonMain", {
     // GENERATED
     files: {
@@ -605,7 +605,7 @@ describe("bundler", () => {
       "/Users/user/project/src/demo-pkg/ext-browser/index.js": `export let browser = 'browser'`,
     },
   });
-  itBundled("packagejson/PackageJsonBrowserIssue2002A", {
+  itBundled("packagejson/PackageJsonBrowserESBuildIssue2002A", {
     // GENERATED
     files: {
       "/Users/user/project/src/entry.js": `require('pkg/sub')`,
@@ -621,7 +621,7 @@ describe("bundler", () => {
       "/Users/user/project/src/node_modules/sub/bar.js": `works()`,
     },
   });
-  itBundled("packagejson/PackageJsonBrowserIssue2002B", {
+  itBundled("packagejson/PackageJsonBrowserESBuildIssue2002B", {
     // GENERATED
     files: {
       "/Users/user/project/src/entry.js": `require('pkg/sub')`,
@@ -637,7 +637,7 @@ describe("bundler", () => {
       "/Users/user/project/src/node_modules/pkg/sub/bar.js": `works()`,
     },
   });
-  itBundled("packagejson/PackageJsonBrowserIssue2002C", {
+  itBundled("packagejson/PackageJsonBrowserESBuildIssue2002C", {
     // GENERATED
     files: {
       "/Users/user/project/src/entry.js": `require('pkg/sub')`,
@@ -1857,7 +1857,7 @@ describe("bundler", () => {
   NOTE: Node's package format requires that CommonJS files in a "type": "module" package use the ".cjs" file extension.
   `, */
   });
-  itBundled("packagejson/PackageJsonNodePathsIssue2752", {
+  itBundled("packagejson/PackageJsonNodePathsESBuildIssue2752", {
     // GENERATED
     files: {
       "/src/entry.js": /* js */ `
diff --git a/test/bundler/esbuild/splitting.test.ts b/test/bundler/esbuild/splitting.test.ts
index 72d0d70de..1dc2c3d11 100644
--- a/test/bundler/esbuild/splitting.test.ts
+++ b/test/bundler/esbuild/splitting.test.ts
@@ -1,4 +1,4 @@
-import { itBundled, testForFile } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, itBundled, testForFile } from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -31,7 +31,7 @@ describe("bundler", () => {
       "/out/b.js": "123",
     },
   });
-  return;
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("splitting/SplittingSharedCommonJSIntoES6", {
     // GENERATED
     files: {
@@ -152,7 +152,7 @@ describe("bundler", () => {
     splitting: true,
     format: "esm",
   });
-  itBundled("splitting/SplittingCircularReferenceIssue251", {
+  itBundled("splitting/SplittingCircularReferenceESBuildIssue251", {
     // GENERATED
     files: {
       "/a.js": /* js */ `
@@ -195,7 +195,7 @@ describe("bundler", () => {
     /* TODO FIX expectedCompileLog: `common.js: WARNING: Import "missing" will always be undefined because the file "empty.js" has no exports
   `, */
   });
-  itBundled("splitting/SplittingReExportIssue273", {
+  itBundled("splitting/SplittingReExportESBuildIssue273", {
     // GENERATED
     files: {
       "/a.js": `export const a = 1`,
@@ -205,7 +205,7 @@ describe("bundler", () => {
     splitting: true,
     format: "esm",
   });
-  itBundled("splitting/SplittingDynamicImportIssue272", {
+  itBundled("splitting/SplittingDynamicImportESBuildIssue272", {
     // GENERATED
     files: {
       "/a.js": `import('./b')`,
@@ -215,7 +215,7 @@ describe("bundler", () => {
     splitting: true,
     format: "esm",
   });
-  itBundled("splitting/SplittingDynamicImportOutsideSourceTreeIssue264", {
+  itBundled("splitting/SplittingDynamicImportOutsideSourceTreeESBuildIssue264", {
     // GENERATED
     files: {
       "/Users/user/project/src/entry1.js": `import('package')`,
@@ -310,7 +310,7 @@ describe("bundler", () => {
     minifyWhitespace: true,
     format: "esm",
   });
-  itBundled("splitting/SplittingMinifyIdentifiersCrashIssue437", {
+  itBundled("splitting/SplittingMinifyIdentifiersCrashESBuildIssue437", {
     // GENERATED
     files: {
       "/a.js": /* js */ `
@@ -329,7 +329,7 @@ describe("bundler", () => {
     minifyIdentifiers: true,
     format: "esm",
   });
-  itBundled("splitting/SplittingHybridESMAndCJSIssue617", {
+  itBundled("splitting/SplittingHybridESMAndCJSESBuildIssue617", {
     // GENERATED
     files: {
       "/a.js": `export let foo`,
@@ -358,7 +358,7 @@ describe("bundler", () => {
     format: "esm",
     splitting: true,
   });
-  itBundled("splitting/EdgeCaseIssue2793WithSplitting", {
+  itBundled("splitting/EdgeCaseESBuildIssue2793WithSplitting", {
     // GENERATED
     files: {
       "/src/a.js": `export const A = 42;`,
@@ -373,7 +373,7 @@ describe("bundler", () => {
     format: "esm",
     splitting: true,
   });
-  itBundled("splitting/EdgeCaseIssue2793WithoutSplitting", {
+  itBundled("splitting/EdgeCaseESBuildIssue2793WithoutSplitting", {
     // GENERATED
     files: {
       "/src/a.js": `export const A = 42;`,
diff --git a/test/bundler/esbuild/ts.test.ts b/test/bundler/esbuild/ts.test.ts
index 5678edc1e..a3ac313a4 100644
--- a/test/bundler/esbuild/ts.test.ts
+++ b/test/bundler/esbuild/ts.test.ts
@@ -1,5 +1,5 @@
 import assert from "assert";
-import { itBundled, testForFile } from "../expectBundled";
+import { RUN_UNCHECKED_TESTS, itBundled, testForFile } from "../expectBundled";
 var { describe, test, expect } = testForFile(import.meta.path);
 
 // Tests ported from:
@@ -393,18 +393,12 @@ describe("bundler", () => {
       const b = api.readFile("/out/b.js");
 
       // make sure the minification trick "enum[enum.K=V]=K" is used, but `enum`
-      assert(a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.A=0]=["']A["']\b/), "should be using enum minification trick (1)");
-      assert(a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.B=1]=["']B["']\b/), "should be using enum minification trick (2)");
-      assert(
-        a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.C=[a-zA-Z$]]=["']C["']\b/),
-        "should be using enum minification trick (3)",
-      );
-      assert(b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.X=0]=["']X["']\b/), "should be using enum minification trick (4)");
-      assert(b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.Y=1]=["']Y["']\b/), "should be using enum minification trick (5)");
-      assert(
-        b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.Z=[a-zA-Z$]]=["']Z["']\b/),
-        "should be using enum minification trick (6)",
-      );
+      assert(a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.A=0]=["']A["']/), "should be using enum minification trick (1)");
+      assert(a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.B=1]=["']B["']/), "should be using enum minification trick (2)");
+      assert(a.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.C=[a-zA-Z$]]=["']C["']/), "should be using enum minification trick (3)");
+      assert(b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.X=0]=["']X["']/), "should be using enum minification trick (4)");
+      assert(b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.Y=1]=["']Y["']/), "should be using enum minification trick (5)");
+      assert(b.match(/\b[a-zA-Z$]\[[a-zA-Z$]\.Z=[a-zA-Z$]]=["']Z["']/), "should be using enum minification trick (6)");
     },
     runtimeFiles: {
       "/test.js": /* js */ `
@@ -426,7 +420,7 @@ describe("bundler", () => {
       `,
     },
   });
-  const TSMinifyNestedEnum = itBundled("ts/TSMinifyNestedEnum", {
+  itBundled("ts/TSMinifyNestedEnum", {
     files: {
       "/a.ts": `function foo(arg) { enum Foo { A, B, C = Foo, D = arg } return Foo }\ncapture(foo)`,
       "/b.ts": `export function foo(arg) { enum Foo { X, Y, Z = Foo, W = arg } return Foo }`,
@@ -508,9 +502,7 @@ describe("bundler", () => {
       assert(!b.includes("=>"), "b should not use arrow");
     },
   });
-  return;
   itBundled("ts/TSMinifyNamespace", {
-    // GENERATED
     files: {
       "/a.ts": /* ts */ `
         namespace Foo {
@@ -518,6 +510,7 @@ describe("bundler", () => {
             foo(Foo, Bar)
           }
         }
+        capture(Foo)
       `,
       "/b.ts": /* ts */ `
         export namespace Foo {
@@ -532,9 +525,22 @@ describe("bundler", () => {
     minifyWhitespace: true,
     minifyIdentifiers: true,
     mode: "transform",
+    onAfterBundle(api) {
+      api.writeFile("/out/a.edited.js", api.readFile("/out/a.js").replace(/capture\((.*?)\)/, `export const Foo = $1`));
+    },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        let called = false;
+        globalThis.foo = (a, b) => called = true;
+        await import('./out/a.edited.js');
+        assert(called, 'foo should be called from a.ts');
+        called = false;
+        await import('./out/b.js');
+        assert(called, 'foo should be called from b.ts');
+      `,
+    },
   });
   itBundled("ts/TSMinifyNamespaceNoLogicalAssignment", {
-    // GENERATED
     files: {
       "/a.ts": /* ts */ `
         namespace Foo {
@@ -558,9 +564,16 @@ describe("bundler", () => {
     outdir: "/",
     mode: "transform",
     unsupportedJSFeatures: ["logical-assignment"],
+    onAfterBundle(api) {
+      const a = api.readFile("/a.js");
+      assert(a.includes("Bar"), "a should not be empty");
+      assert(!a.includes("||="), "a should not use logical assignment");
+      const b = api.readFile("/b.js");
+      assert(b.includes("Bar"), "b should not be empty");
+      assert(!b.includes("||="), "b should not use logical assignment");
+    },
   });
   itBundled("ts/TSMinifyNamespaceNoArrow", {
-    // GENERATED
     files: {
       "/a.ts": /* ts */ `
         namespace Foo {
@@ -583,9 +596,17 @@ describe("bundler", () => {
     minifyIdentifiers: true,
     outdir: "/",
     mode: "transform",
+    unsupportedJSFeatures: ["arrow"],
+    onAfterBundle(api) {
+      const a = api.readFile("/a.js");
+      assert(a.includes("foo"), "a should not be empty");
+      assert(!a.includes("=>"), "a should not use arrow");
+      const b = api.readFile("/b.js");
+      assert(b.includes("foo"), "b should not be empty");
+      assert(!b.includes("=>"), "b should not use arrow");
+    },
   });
   itBundled("ts/TSMinifyDerivedClass", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         class Foo extends Bar {
@@ -597,44 +618,71 @@ describe("bundler", () => {
             bar();
           }
         }
+
+        export {Foo}
       `,
     },
     minifySyntax: true,
-    unsupportedJSFeatures: "es2015",
-    mode: "transform",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        let calledFoo = false;
+        let calledBar = false;
+        globalThis.foo = () => calledFoo = true;
+        globalThis.bar = () => calledBar = true;
+        globalThis.Bar = class Bar {
+          constructor() {
+            console.log('super')
+            this.hello = 3;
+          }
+        };
+        const {Foo} = await import('./entry.js');
+        import assert from 'assert';
+        const instance = new Foo();
+        console.log(instance.foo, instance.bar, instance.hello);
+        assert(calledFoo, 'foo should be called');
+        assert(calledBar, 'bar should be called');
+      `,
+    },
+    run: {
+      file: "/test.js",
+      stdout: "super\n1 2 3",
+    },
   });
   itBundled("ts/TSImportVsLocalCollisionAllTypes", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import {a, b, c, d, e} from './other.ts'
         let a
         const b = 0
         var c
-        function d() {}
-        class e {}
-        console.log(a, b, c, d, e)
+        function d() { return 5; }
+        class e { constructor() { this.prop = 2; }}
+        console.log(JSON.stringify([a, b, c, d(), new e]))
       `,
       "/other.ts": ``,
     },
+    run: {
+      stdout: '[null,0,null,5,{"prop":2}]',
+    },
   });
   itBundled("ts/TSImportVsLocalCollisionMixed", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import {a, b, c, d, e, real} from './other.ts'
         let a
         const b = 0
         var c
-        function d() {}
-        class e {}
-        console.log(a, b, c, d, e, real)
+        function d() { return 5; }
+        class e { constructor() { this.prop = 2; }}
+        console.log(JSON.stringify([a, b, c, d(), new e, real]))
       `,
       "/other.ts": `export let real = 123`,
     },
+    run: {
+      stdout: '[null,0,null,5,{"prop":2},123]',
+    },
   });
   itBundled("ts/TSImportEqualsEliminationTest", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import a = foo.a
@@ -648,44 +696,62 @@ describe("bundler", () => {
         export let bar = c
       `,
     },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.foo = {
+          a: { b: { c: 123 } },
+          get x() {
+            throw new Error('should not be called')
+          }
+        };
+        const {bar} = await import('./out.js');
+        console.log(bar);
+      `,
+    },
+    run: {
+      file: "/test.js",
+      stdout: "123",
+    },
   });
   itBundled("ts/TSImportEqualsTreeShakingFalse", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import { foo } from 'pkg'
         import used = foo.used
-        import unused = foo.unused
+        import unused_keep = foo.unused
         export { used }
       `,
     },
-    mode: "passthrough",
+    treeShaking: false,
+    dce: true,
+    mode: "transform",
   });
   itBundled("ts/TSImportEqualsTreeShakingTrue", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import { foo } from 'pkg'
         import used = foo.used
-        import unused = foo.unused
+        import unused_drop = foo.unused
         export { used }
       `,
     },
-    mode: "passthrough",
+    dce: true,
+    treeShaking: true,
+    mode: "transform",
   });
   itBundled("ts/TSImportEqualsBundle", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import { foo } from 'pkg'
         import used = foo.used
-        import unused = foo.unused
+        import unused_drop = foo.unused
         export { used }
       `,
     },
+    dce: true,
+    external: ["pkg"],
   });
   itBundled("ts/TSMinifiedBundleES6", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import {foo} from './a'
@@ -700,13 +766,15 @@ describe("bundler", () => {
     minifySyntax: true,
     minifyWhitespace: true,
     minifyIdentifiers: true,
+    run: {
+      stdout: "123",
+    },
   });
   itBundled("ts/TSMinifiedBundleCommonJS", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         const {foo} = require('./a')
-        console.log(foo(), require('./j.json'))
+        console.log(JSON.stringify([foo(), require('./j.json')]))
       `,
       "/a.ts": /* ts */ `
         exports.foo = function() {
@@ -718,9 +786,38 @@ describe("bundler", () => {
     minifySyntax: true,
     minifyWhitespace: true,
     minifyIdentifiers: true,
+    run: {
+      stdout: '[123,{"test":true}]',
+    },
+  });
+  // TODO: all situations with decorators are currently not runtime-checked. as of writing bun crashes when hitting them at all.
+  itBundled("ts/TypeScriptDecoratorsSimpleCase", {
+    files: {
+      "/entry.ts": /* ts */ `
+        function decorator(...args) {
+          console.log('decorator called', JSON.stringify(args))
+        }
+
+        @decorator
+        class Foo {
+          @decorator
+          bar() {
+            console.log('bar called')
+          }
+        }
+
+        new Foo().bar()
+      `,
+    },
+    run: {
+      stdout: `
+        decorator called [{},"bar",{"writable":true,"enumerable":false,"configurable":true}]
+        decorator called [null]
+        bar called
+      `,
+    },
   });
   itBundled("ts/TypeScriptDecorators", {
-    // GENERATED
     files: {
       "/entry.js": /* js */ `
         import all from './all'
@@ -859,19 +956,17 @@ describe("bundler", () => {
     },
   });
   itBundled("ts/TypeScriptDecoratorsKeepNames", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         @decoratorMustComeAfterName
         class Foo {}
       `,
     },
+    keepNames: true,
   });
-  itBundled("ts/TypeScriptDecoratorScopeIssue2147", {
-    // GENERATED
+  itBundled("ts/TypeScriptDecoratorScopeESBuildIssue2147", {
     files: {
       "/entry.ts": /* ts */ `
-        let foo = 1
         class Foo {
           method1(@dec(foo) foo = 2) {}
           method2(@dec(() => foo) foo = 3) {}
@@ -880,7 +975,6 @@ describe("bundler", () => {
         class Bar {
           static x = class {
             static y = () => {
-              let bar = 1
               @dec(bar)
               @dec(() => bar)
               class Baz {
@@ -895,10 +989,22 @@ describe("bundler", () => {
         }
       `,
     },
-    mode: "passthrough",
+    mode: "transform",
+    onAfterBundle(api) {
+      const capturedCalls = api.captureFile("/out.js", "dec");
+      expect(capturedCalls).toEqual([
+        "foo",
+        "() => foo",
+        "bar",
+        "() => bar",
+        "() => bar",
+        "() => bar",
+        "bar",
+        "() => bar",
+      ]);
+    },
   });
-  itBundled("ts/TSExportDefaultTypeIssue316", {
-    // GENERATED
+  itBundled("ts/TSExportDefaultTypeESBuildIssue316", {
     files: {
       "/entry.ts": /* ts */ `
         import dc_def, { bar as dc } from './keep/declare-class'
@@ -1017,9 +1123,23 @@ describe("bundler", () => {
         export let bar = 123
       `,
     },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.foo = 123456;
+        const mod = (await import('./out.js')).default;
+        console.log(JSON.stringify(mod))
+        console.log(JSON.stringify(mod.map(x => typeof x)))
+      `,
+    },
+    run: {
+      file: "/test.js",
+      stdout: `
+        [123456,123,123456,123,null,123,123456,123,123456,123,{"num":0},123,{"num":0},123,123,123,123,123,123,123]
+        ["number","number","number","number","function","number","number","number","number","number","object","number","object","number","number","number","number","number","number","number"]
+      `,
+    },
   });
   itBundled("ts/TSImplicitExtensions", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import './pick-js.js'
@@ -1030,21 +1150,23 @@ describe("bundler", () => {
         import './order-jsx.jsx'
       `,
       "/pick-js.js": `console.log("correct")`,
-      "/pick-js.ts": `console.log("wrong")`,
-      "/pick-ts.jsx": `console.log("wrong")`,
+      "/pick-js.ts": `console.log("FAILED")`,
+      "/pick-ts.jsx": `console.log("FAILED")`,
       "/pick-ts.ts": `console.log("correct")`,
       "/pick-jsx.jsx": `console.log("correct")`,
-      "/pick-jsx.tsx": `console.log("wrong")`,
-      "/pick-tsx.js": `console.log("wrong")`,
+      "/pick-jsx.tsx": `console.log("FAILED")`,
+      "/pick-tsx.js": `console.log("FAILED")`,
       "/pick-tsx.tsx": `console.log("correct")`,
       "/order-js.ts": `console.log("correct")`,
-      "/order-js.tsx": `console.log("wrong")`,
+      "/order-js.tsx": `console.log("FAILED")`,
       "/order-jsx.ts": `console.log("correct")`,
-      "/order-jsx.tsx": `console.log("wrong")`,
+      "/order-jsx.tsx": `console.log("FAILED")`,
+    },
+    run: {
+      stdout: "correct\n".repeat(6),
     },
   });
   itBundled("ts/TSImplicitExtensionsMissing", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import './mjs.mjs'
@@ -1059,21 +1181,23 @@ describe("bundler", () => {
       "/js.ts.js": ``,
       "/jsx.tsx.jsx": ``,
     },
-    /* TODO FIX expectedScanLog: `entry.ts: ERROR: Could not resolve "./mjs.mjs"
-  entry.ts: ERROR: Could not resolve "./cjs.cjs"
-  entry.ts: ERROR: Could not resolve "./js.js"
-  entry.ts: ERROR: Could not resolve "./jsx.jsx"
-  `, */
+    bundleErrors: {
+      "/entry.ts": [
+        `Could not resolve: "./mjs.mjs"`,
+        `Could not resolve: "./cjs.cjs"`,
+        `Could not resolve: "./js.js"`,
+        `Could not resolve: "./jsx.jsx"`,
+      ],
+    },
   });
-  itBundled("ts/ExportTypeIssue379", {
-    // GENERATED
+  itBundled("ts/ExportTypeESBuildIssue379", {
     files: {
       "/entry.ts": /* ts */ `
         import * as A from './a'
         import * as B from './b'
         import * as C from './c'
         import * as D from './d'
-        console.log(A, B, C, D)
+        console.log(JSON.stringify([A, B, C, D]))
       `,
       "/a.ts": /* ts */ `
         type Test = Element
@@ -1098,135 +1222,284 @@ describe("bundler", () => {
       `,
       "/test.ts": `export type Test = Element`,
     },
+    run: {
+      stdout: '[{"foo":123},{"foo":123},{"foo":123},{"foo":123}]',
+    },
+    useDefineForClassFields: false,
   });
   itBundled("ts/ThisInsideFunctionTS", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
-        function foo(x = this) { console.log(this) }
+        function foo(x = this) { return [x, this]; }
         const objFoo = {
-          foo(x = this) { console.log(this) }
+          foo(x = this) { return [x, this]; }
         }
         class Foo {
           x = this
-          static y = this.z
-          foo(x = this) { console.log(this) }
-          static bar(x = this) { console.log(this) }
+          static z = 456;
+          static y = this.z;
+          foo(x = this) { return [x, this]; }
+          static bar(x = this) { return [x, this]; }
         }
-        new Foo(foo(objFoo))
+
+        assert.deepEqual(foo('bun'), ['bun', undefined]);
+        assert.deepEqual(foo.call('this'), ['this', 'this']);
+        assert.deepEqual(foo.call('this', 'bun'), ['bun', 'this']);
+        assert.deepEqual(objFoo.foo('bun'), ['bun', objFoo]);
+        assert.deepEqual(objFoo.foo(), [objFoo, objFoo]);
+        const fooInstance = new Foo();
+        assert(fooInstance.x === fooInstance, 'Foo#x');
+        assert(Foo.y === 456, 'Foo.y');
+        assert.deepEqual(Foo.bar('bun'), ['bun', Foo]);
+        assert.deepEqual(Foo.bar(), [Foo, Foo]);
+        assert.deepEqual(fooInstance.foo(), [fooInstance, fooInstance]);
+        assert.deepEqual(fooInstance.foo('bun'), ['bun', fooInstance]);
+
         if (nested) {
-          function bar(x = this) { console.log(this) }
+          function bar(x = this) { return [x, this]; }
           const objBar = {
-            foo(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
           }
           class Bar {
             x = this
+            static z = 456;
             static y = this.z
-            foo(x = this) { console.log(this) }
-            static bar(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
+            static bar(x = this) { return [x, this]; }
           }
-          new Bar(bar(objBar))
+          
+          assert.deepEqual(bar('bun'), ['bun', undefined]);
+          assert.deepEqual(bar.call('this'), ['this', 'this']);
+          assert.deepEqual(bar.call('this', 'bun'), ['bun', 'this']);
+          assert.deepEqual(objBar.foo('bun'), ['bun', objBar]);
+          assert.deepEqual(objBar.foo(), [objBar, objBar]);
+          const barInstance = new Bar();
+          assert(barInstance.x === barInstance, 'Bar#x');
+          assert(Bar.y === 456, 'Bar.y');
+          assert.deepEqual(Bar.bar('bun'), ['bun', Bar]);
+          assert.deepEqual(Bar.bar(), [Bar, Bar]);
+          assert.deepEqual(barInstance.foo(), [barInstance, barInstance]);
+          assert.deepEqual(barInstance.foo('bun'), ['bun', barInstance]);
         }
       `,
     },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.nested = true;
+        globalThis.assert = (await import('assert')).default;
+        import('./out')
+      `,
+    },
+    run: {
+      file: "/test.js",
+    },
   });
   itBundled("ts/ThisInsideFunctionTSUseDefineForClassFields", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
-        function foo(x = this) { console.log(this) }
+        function foo(x = this) { return [x, this]; }
         const objFoo = {
-          foo(x = this) { console.log(this) }
+          foo(x = this) { return [x, this]; }
         }
         class Foo {
           x = this
-          static y = this.z
-          foo(x = this) { console.log(this) }
-          static bar(x = this) { console.log(this) }
+          static z = 456;
+          static y = this.z;
+          foo(x = this) { return [x, this]; }
+          static bar(x = this) { return [x, this]; }
         }
-        new Foo(foo(objFoo))
+
+        assert.deepEqual(foo('bun'), ['bun', undefined]);
+        assert.deepEqual(foo.call('this'), ['this', 'this']);
+        assert.deepEqual(foo.call('this', 'bun'), ['bun', 'this']);
+        assert.deepEqual(objFoo.foo('bun'), ['bun', objFoo]);
+        assert.deepEqual(objFoo.foo(), [objFoo, objFoo]);
+        const fooInstance = new Foo();
+        assert(fooInstance.x === fooInstance, 'Foo#x');
+        assert(Foo.y === 456, 'Foo.y');
+        assert.deepEqual(Foo.bar('bun'), ['bun', Foo]);
+        assert.deepEqual(Foo.bar(), [Foo, Foo]);
+        assert.deepEqual(fooInstance.foo(), [fooInstance, fooInstance]);
+        assert.deepEqual(fooInstance.foo('bun'), ['bun', fooInstance]);
+
         if (nested) {
-          function bar(x = this) { console.log(this) }
+          function bar(x = this) { return [x, this]; }
           const objBar = {
-            foo(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
           }
           class Bar {
             x = this
+            static z = 456;
             static y = this.z
-            foo(x = this) { console.log(this) }
-            static bar(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
+            static bar(x = this) { return [x, this]; }
           }
-          new Bar(bar(objBar))
+          
+          assert.deepEqual(bar('bun'), ['bun', undefined]);
+          assert.deepEqual(bar.call('this'), ['this', 'this']);
+          assert.deepEqual(bar.call('this', 'bun'), ['bun', 'this']);
+          assert.deepEqual(objBar.foo('bun'), ['bun', objBar]);
+          assert.deepEqual(objBar.foo(), [objBar, objBar]);
+          const barInstance = new Bar();
+          assert(barInstance.x === barInstance, 'Bar#x');
+          assert(Bar.y === 456, 'Bar.y');
+          assert.deepEqual(Bar.bar('bun'), ['bun', Bar]);
+          assert.deepEqual(Bar.bar(), [Bar, Bar]);
+          assert.deepEqual(barInstance.foo(), [barInstance, barInstance]);
+          assert.deepEqual(barInstance.foo('bun'), ['bun', barInstance]);
         }
       `,
     },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.nested = true;
+        globalThis.assert = (await import('assert')).default;
+        import('./out')
+      `,
+    },
+    run: {
+      file: "/test.js",
+    },
+    useDefineForClassFields: true,
   });
   itBundled("ts/ThisInsideFunctionTSNoBundle", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
-        function foo(x = this) { console.log(this) }
+        function foo(x = this) { return [x, this]; }
         const objFoo = {
-          foo(x = this) { console.log(this) }
+          foo(x = this) { return [x, this]; }
         }
         class Foo {
           x = this
-          static y = this.z
-          foo(x = this) { console.log(this) }
-          static bar(x = this) { console.log(this) }
+          static z = 456;
+          static y = this.z;
+          foo(x = this) { return [x, this]; }
+          static bar(x = this) { return [x, this]; }
         }
-        new Foo(foo(objFoo))
+
+        assert.deepEqual(foo('bun'), ['bun', undefined]);
+        assert.deepEqual(foo.call('this'), ['this', 'this']);
+        assert.deepEqual(foo.call('this', 'bun'), ['bun', 'this']);
+        assert.deepEqual(objFoo.foo('bun'), ['bun', objFoo]);
+        assert.deepEqual(objFoo.foo(), [objFoo, objFoo]);
+        const fooInstance = new Foo();
+        assert(fooInstance.x === fooInstance, 'Foo#x');
+        assert(Foo.y === 456, 'Foo.y');
+        assert.deepEqual(Foo.bar('bun'), ['bun', Foo]);
+        assert.deepEqual(Foo.bar(), [Foo, Foo]);
+        assert.deepEqual(fooInstance.foo(), [fooInstance, fooInstance]);
+        assert.deepEqual(fooInstance.foo('bun'), ['bun', fooInstance]);
+
         if (nested) {
-          function bar(x = this) { console.log(this) }
+          function bar(x = this) { return [x, this]; }
           const objBar = {
-            foo(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
           }
           class Bar {
             x = this
+            static z = 456;
             static y = this.z
-            foo(x = this) { console.log(this) }
-            static bar(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
+            static bar(x = this) { return [x, this]; }
           }
-          new Bar(bar(objBar))
+          
+          assert.deepEqual(bar('bun'), ['bun', undefined]);
+          assert.deepEqual(bar.call('this'), ['this', 'this']);
+          assert.deepEqual(bar.call('this', 'bun'), ['bun', 'this']);
+          assert.deepEqual(objBar.foo('bun'), ['bun', objBar]);
+          assert.deepEqual(objBar.foo(), [objBar, objBar]);
+          const barInstance = new Bar();
+          assert(barInstance.x === barInstance, 'Bar#x');
+          assert(Bar.y === 456, 'Bar.y');
+          assert.deepEqual(Bar.bar('bun'), ['bun', Bar]);
+          assert.deepEqual(Bar.bar(), [Bar, Bar]);
+          assert.deepEqual(barInstance.foo(), [barInstance, barInstance]);
+          assert.deepEqual(barInstance.foo('bun'), ['bun', barInstance]);
         }
       `,
     },
-    mode: "passthrough",
+    mode: "transform",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.nested = true;
+        globalThis.assert = (await import('assert')).default;
+        import('./out')
+      `,
+    },
+    run: {
+      file: "/test.js",
+    },
   });
   itBundled("ts/ThisInsideFunctionTSNoBundleUseDefineForClassFields", {
     // GENERATED
     files: {
       "/entry.ts": /* ts */ `
-        function foo(x = this) { console.log(this) }
+        function foo(x = this) { return [x, this]; }
         const objFoo = {
-          foo(x = this) { console.log(this) }
+          foo(x = this) { return [x, this]; }
         }
         class Foo {
           x = this
-          static y = this.z
-          foo(x = this) { console.log(this) }
-          static bar(x = this) { console.log(this) }
+          static z = 456;
+          static y = this.z;
+          foo(x = this) { return [x, this]; }
+          static bar(x = this) { return [x, this]; }
         }
-        new Foo(foo(objFoo))
+
+        assert.deepEqual(foo('bun'), ['bun', undefined]);
+        assert.deepEqual(foo.call('this'), ['this', 'this']);
+        assert.deepEqual(foo.call('this', 'bun'), ['bun', 'this']);
+        assert.deepEqual(objFoo.foo('bun'), ['bun', objFoo]);
+        assert.deepEqual(objFoo.foo(), [objFoo, objFoo]);
+        const fooInstance = new Foo();
+        assert(fooInstance.x === fooInstance, 'Foo#x');
+        assert(Foo.y === 456, 'Foo.y');
+        assert.deepEqual(Foo.bar('bun'), ['bun', Foo]);
+        assert.deepEqual(Foo.bar(), [Foo, Foo]);
+        assert.deepEqual(fooInstance.foo(), [fooInstance, fooInstance]);
+        assert.deepEqual(fooInstance.foo('bun'), ['bun', fooInstance]);
+
         if (nested) {
-          function bar(x = this) { console.log(this) }
+          function bar(x = this) { return [x, this]; }
           const objBar = {
-            foo(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
           }
           class Bar {
             x = this
+            static z = 456;
             static y = this.z
-            foo(x = this) { console.log(this) }
-            static bar(x = this) { console.log(this) }
+            foo(x = this) { return [x, this]; }
+            static bar(x = this) { return [x, this]; }
           }
-          new Bar(bar(objBar))
+          
+          assert.deepEqual(bar('bun'), ['bun', undefined]);
+          assert.deepEqual(bar.call('this'), ['this', 'this']);
+          assert.deepEqual(bar.call('this', 'bun'), ['bun', 'this']);
+          assert.deepEqual(objBar.foo('bun'), ['bun', objBar]);
+          assert.deepEqual(objBar.foo(), [objBar, objBar]);
+          const barInstance = new Bar();
+          assert(barInstance.x === barInstance, 'Bar#x');
+          assert(Bar.y === 456, 'Bar.y');
+          assert.deepEqual(Bar.bar('bun'), ['bun', Bar]);
+          assert.deepEqual(Bar.bar(), [Bar, Bar]);
+          assert.deepEqual(barInstance.foo(), [barInstance, barInstance]);
+          assert.deepEqual(barInstance.foo('bun'), ['bun', barInstance]);
         }
       `,
     },
-    mode: "passthrough",
+    mode: "transform",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.nested = true;
+        globalThis.assert = (await import('assert')).default;
+        import('./out')
+      `,
+    },
+    run: {
+      file: "/test.js",
+    },
   });
   itBundled("ts/TSComputedClassFieldUseDefineFalse", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         class Foo {
@@ -1237,13 +1510,43 @@ describe("bundler", () => {
           @dec
           [y] = z;
         }
-        new Foo()
+        export default Foo;
       `,
     },
-    mode: "passthrough",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.q = 'q1';
+        globalThis.r = 'r1';
+        globalThis.s = 's1';
+        globalThis.x = 'x1';
+        globalThis.y = 'y1';
+        globalThis.z = 'z1';
+        globalThis.dec = function(...args) {
+          console.log(JSON.stringify([this, ...args]));
+        };
+        const Foo = (await import('./out')).default;
+        globalThis.q = 'q2';
+        globalThis.r = 'r2';
+        globalThis.s = 's2';
+        globalThis.x = 'x2';
+        globalThis.y = 'y2';
+        globalThis.z = 'z2';
+        const y = new Foo();
+        console.log(JSON.stringify(y));
+      `,
+    },
+    useDefineForClassFields: false,
+    mode: "transform",
+    run: {
+      stdout: `
+        [null,{},"x1",null]
+        [null,{},"y1",null]
+        {"r1":"s2","y1":"z2"}
+      `,
+      file: "/test.js",
+    },
   });
   itBundled("ts/TSComputedClassFieldUseDefineTrue", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         class Foo {
@@ -1254,13 +1557,43 @@ describe("bundler", () => {
           @dec
           [y] = z;
         }
-        new Foo()
+        export default Foo;
       `,
     },
-    mode: "passthrough",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.q = 'q1';
+        globalThis.r = 'r1';
+        globalThis.s = 's1';
+        globalThis.x = 'x1';
+        globalThis.y = 'y1';
+        globalThis.z = 'z1';
+        globalThis.dec = function(...args) {
+          console.log(JSON.stringify([this, ...args]));
+        };
+        const Foo = (await import('./out')).default;
+        globalThis.q = 'q2';
+        globalThis.r = 'r2';
+        globalThis.s = 's2';
+        globalThis.x = 'x2';
+        globalThis.y = 'y2';
+        globalThis.z = 'z2';
+        const y = new Foo();
+        console.log(JSON.stringify(y));
+      `,
+    },
+    useDefineForClassFields: true,
+    mode: "transform",
+    run: {
+      stdout: `
+        [null,{},"x1",null]
+        [null,{},"y1",null]
+        {"r1":"s2","y1":"z2"}
+      `,
+      file: "/test.js",
+    },
   });
   itBundled("ts/TSComputedClassFieldUseDefineTrueLower", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         class Foo {
@@ -1271,14 +1604,44 @@ describe("bundler", () => {
           @dec
           [y] = z;
         }
-        new Foo()
+        export default Foo;
+      `,
+    },
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        globalThis.q = 'q1';
+        globalThis.r = 'r1';
+        globalThis.s = 's1';
+        globalThis.x = 'x1';
+        globalThis.y = 'y1';
+        globalThis.z = 'z1';
+        globalThis.dec = function(...args) {
+          console.log(JSON.stringify([this, ...args]));
+        };
+        const Foo = (await import('./out')).default;
+        globalThis.q = 'q2';
+        globalThis.r = 'r2';
+        globalThis.s = 's2';
+        globalThis.x = 'x2';
+        globalThis.y = 'y2';
+        globalThis.z = 'z2';
+        const y = new Foo();
+        console.log(JSON.stringify(y));
       `,
     },
     useDefineForClassFields: true,
-    mode: "passthrough",
+    mode: "transform",
+    run: {
+      stdout: `
+        [null,{},"x1",null]
+        [null,{},"y1",null]
+        {"r1":"s2","y1":"z2"}
+      `,
+      file: "/test.js",
+    },
+    unsupportedJSFeatures: ["class-field"],
   });
   itBundled("ts/TSAbstractClassFieldUseAssign", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         const keepThis = Symbol('keepThis')
@@ -1288,15 +1651,15 @@ describe("bundler", () => {
           [keepThis]: any
           abstract REMOVE_THIS_TOO: any
           abstract [AND_REMOVE_THIS]: any
-          abstract [(x => y => x + y)('nested')('scopes')]: any
+          abstract [(x => y => x + y)('nested')('scopes_REMOVE')]: any
         }
         (() => new Foo())()
       `,
     },
-    mode: "passthrough",
+    dce: true,
+    useDefineForClassFields: false,
   });
   itBundled("ts/TSAbstractClassFieldUseDefine", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         const keepThisToo = Symbol('keepThisToo')
@@ -1311,24 +1674,28 @@ describe("bundler", () => {
         (() => new Foo())()
       `,
     },
-    mode: "passthrough",
+    mode: "transform",
+    useDefineForClassFields: true,
   });
   itBundled("ts/TSImportMTS", {
-    // GENERATED
     files: {
       "/entry.ts": `import './imported.mjs'`,
       "/imported.mts": `console.log('works')`,
     },
+    run: {
+      stdout: "works",
+    },
   });
   itBundled("ts/TSImportCTS", {
-    // GENERATED
     files: {
       "/entry.ts": `require('./required.cjs')`,
       "/required.cjs": `console.log('works')`,
     },
+    run: {
+      stdout: "works",
+    },
   });
   itBundled("ts/TSSideEffectsFalseWarningTypeDeclarations", {
-    // GENERATED
     files: {
       "/entry.ts": /* ts */ `
         import "some-js"
@@ -1348,14 +1715,11 @@ describe("bundler", () => {
       "/node_modules/empty-dts/package.json": `{ "main": "./foo.d.ts", "sideEffects": false }`,
       "/node_modules/empty-dts/foo.d.ts": `export type Foo = number`,
     },
-    /* TODO FIX expectedScanLog: `entry.ts: WARNING: Ignoring this import because "node_modules/some-js/foo.js" was marked as having no side effects
-  node_modules/some-js/package.json: NOTE: "sideEffects" is false in the enclosing "package.json" file:
-  entry.ts: WARNING: Ignoring this import because "node_modules/some-ts/foo.ts" was marked as having no side effects
-  node_modules/some-ts/package.json: NOTE: "sideEffects" is false in the enclosing "package.json" file:
-  `, */
+    onAfterBundle(api) {
+      expect(api.readFile("/out.js").trim()).toBe("");
+    },
   });
   itBundled("ts/TSSiblingNamespace", {
-    // GENERATED
     files: {
       "/let.ts": /* ts */ `
         export namespace x { export let y = 123 }
@@ -1379,8 +1743,24 @@ describe("bundler", () => {
       `,
     },
     entryPoints: ["/let.ts", "/function.ts", "/class.ts", "/namespace.ts", "/enum.ts"],
-    mode: "passthrough",
+    mode: "transform",
+    runtimeFiles: {
+      "/test.js": /* js */ `
+        import assert from 'assert'
+        const test_let = (await import('./let.js')).x
+        assert(test_let.x === test_let.x, "let.ts worked")
+        const test_function = (await import('./function.js')).x
+        assert(test_function.x === test_function.x, "function.ts worked")
+        const test_class = (await import('./class.js')).x
+        assert(test_class.x === test_class.x, "class.ts worked")
+        const test_namespace = (await import('./namespace.js')).x
+        assert(test_namespace.x === test_namespace.x, "namespace.ts worked")
+        const test_enum = (await import('./enum.js')).x
+        assert(test_enum.x === test_enum.x, "enum.ts worked")
+      `,
+    },
   });
+  if (!RUN_UNCHECKED_TESTS) return;
   itBundled("ts/TSSiblingEnum", {
     // GENERATED
     files: {
diff --git a/test/bundler/expectBundled.md b/test/bundler/expectBundled.md
index 4e944543c..be455910c 100644
--- a/test/bundler/expectBundled.md
+++ b/test/bundler/expectBundled.md
@@ -188,3 +188,23 @@ Places that are not required to be dce'd contain `POSSIBLE_REMOVAL` and do not t
 ## keepNames tricks
 
 In `esbuild/default.test.ts`, test `default/KeepNamesTreeShaking`, we call the esbuild cli to minify identifiers, and then check the code for expected class names to survive the minification (keep names forcibily sets functions `.name`).
+
+# capture
+
+This lets you capture the exact js that is emitted by wrapping it in a function call `capture`. Like a partial snapshot.
+
+```ts
+itBundled("minify/TemplateStringFolding", {
+  files: {
+    "/entry.js": /* js */ `
+      capture(\`😋📋👌\`.length)
+      capture(\`😋📋👌\`.length === 6)
+      capture(\`😋📋👌\`.length == 6)
+      capture(\`😋📋👌\`.length === 2)
+      capture(\`😋📋👌\`.length == 2)
+    `,
+  },
+  minifySyntax: true,
+  capture: ["6", "true", "true", "false", "false"],
+});
+```
diff --git a/test/bundler/expectBundled.ts b/test/bundler/expectBundled.ts
index 0b467dddf..3bffb4271 100644
--- a/test/bundler/expectBundled.ts
+++ b/test/bundler/expectBundled.ts
@@ -32,6 +32,16 @@ const DEBUG = process.env.BUN_BUNDLER_TEST_DEBUG;
 const FILTER = process.env.BUN_BUNDLER_TEST_FILTER;
 /** Path to the bun. TODO: Once bundler is merged, we should remove the `bun-debug` fallback. */
 const BUN_EXE = (process.env.BUN_EXE && Bun.which(process.env.BUN_EXE)) ?? Bun.which("bun-debug") ?? bunExe();
+/**
+ * If set to true, run an alternate validation for tests which is much looser.
+ * We are only testing for:
+ * - bundler does not crash
+ * - output js has no syntax errors
+ *
+ * Defaults to true unless you are running a single test.
+ */
+const LOOSE = !process.env.BUN_BUNDLER_TEST_FILTER && process.env.BUN_BUNDLER_TEST_LOOSE !== "false";
+export const RUN_UNCHECKED_TESTS = LOOSE;
 
 const outBaseTemplate = path.join(tmpdir(), "bun-build-tests", `${ESBUILD ? "esbuild" : "bun"}-`);
 if (!existsSync(path.dirname(outBaseTemplate))) mkdirSync(path.dirname(outBaseTemplate), { recursive: true });
@@ -57,7 +67,7 @@ export interface BundlerTestInput {
   entryPointsRaw?: string[];
   /** Defaults to bundle */
   mode?: "bundle" | "transform";
-  /** Used for `default/ErrorMessageCrashStdinIssue2913`. */
+  /** Used for `default/ErrorMessageCrashStdinESBuildIssue2913`. */
   stdin?: { contents: string; cwd: string };
   /** Use when doing something weird with entryPoints and you need to check other output paths. */
   outputPaths?: string[];
@@ -106,6 +116,7 @@ export interface BundlerTestInput {
   treeShaking?: boolean;
   unsupportedCSSFeatures?: string[];
   unsupportedJSFeatures?: string[];
+  /** if set to true or false, create or edit tsconfig.json to set compilerOptions.useDefineForClassFields */
   useDefineForClassFields?: boolean;
   sourceMap?: boolean | "inline" | "external";
 
@@ -152,6 +163,9 @@ export interface BundlerTestInput {
     files: string[];
   };
 
+  /** Captures `capture()` function calls in the output. */
+  capture?: string[];
+
   /** Run after bundle happens but before runtime. */
   onAfterBundle?(api: BundlerTestBundleAPI): void;
 }
@@ -167,6 +181,10 @@ export interface BundlerTestBundleAPI {
   appendFile(file: string, contents: string): void;
   expectFile(file: string): Expect;
   assertFileExists(file: string): void;
+  /**
+   * Finds all `capture(...)` calls and returns the strings within each function call.
+   */
+  captureFile(file: string, fnName?: string): string[];
 
   warnings: Record<string, { file: string; error: string; line?: string; col?: string }[]>;
   options: BundlerTestInput;
@@ -220,6 +238,7 @@ export function expectBundled(
     banner,
     bundleErrors,
     bundleWarnings,
+    capture,
     dce,
     dceKeepMarkerCount,
     define,
@@ -236,6 +255,7 @@ export function expectBundled(
     legalComments,
     loader,
     mainFields,
+    matchesReference,
     metafile,
     minifyIdentifiers,
     minifySyntax,
@@ -255,7 +275,7 @@ export function expectBundled(
     treeShaking,
     unsupportedCSSFeatures,
     unsupportedJSFeatures,
-    matchesReference,
+    useDefineForClassFields,
     ...unknownProps
   } = opts;
 
@@ -287,6 +307,12 @@ export function expectBundled(
   if (!ESBUILD && format !== "esm") {
     throw new Error("formats besides esm not implemented in bun build");
   }
+  if (!ESBUILD && platform === "neutral") {
+    throw new Error("platform=neutral not implemented in bun build");
+  }
+  if (!ESBUILD && mode === "transform") {
+    throw new Error("mode=transform not implemented in bun build");
+  }
   if (!ESBUILD && metafile) {
     throw new Error("metafile not implemented in bun build");
   }
@@ -358,6 +384,26 @@ export function expectBundled(
     writeFileSync(filename, dedent(contents).replace(/\{\{root\}\}/g, root));
   }
 
+  if (useDefineForClassFields !== undefined) {
+    if (existsSync(path.join(root, "tsconfig.json"))) {
+      try {
+        const tsconfig = JSON.parse(readFileSync(path.join(root, "tsconfig.json"), "utf8"));
+        tsconfig.compilerOptions = tsconfig.compilerOptions ?? {};
+        tsconfig.compilerOptions.useDefineForClassFields = useDefineForClassFields;
+        writeFileSync(path.join(root, "tsconfig.json"), JSON.stringify(tsconfig, null, 2));
+      } catch (error) {
+        console.log(
+          "DEBUG NOTE: specifying useDefineForClassFields causes tsconfig.json to be parsed as JSON and not JSONC.",
+        );
+      }
+    } else {
+      writeFileSync(
+        path.join(root, "tsconfig.json"),
+        JSON.stringify({ compilerOptions: { useDefineForClassFields } }, null, 2),
+      );
+    }
+  }
+
   // Run bun build cli. In the future we can move to using `Bun.Bundler`
   const cmd = (
     !ESBUILD
@@ -391,6 +437,7 @@ export function expectBundled(
           // keepNames && `--keep-names`,
           // mainFields && `--main-fields=${mainFields}`,
           // loader && Object.entries(loader).map(([k, v]) => ["--loader", `${k}=${v}`]),
+          mode === "transform" && "--transform",
         ]
       : [
           ESBUILD_PATH,
@@ -478,8 +525,9 @@ export function expectBundled(
 
   if (!success) {
     if (!ESBUILD) {
+      const errorText = stderr.toString("utf-8");
       const errorRegex = /^error: (.*?)\n(?:.*?\n\s*\^\s*\n(.*?)\n)?/gms;
-      const allErrors = [...stderr!.toString("utf-8").matchAll(errorRegex)]
+      const allErrors = [...errorText.matchAll(errorRegex)]
         .map(([_str1, error, source]) => {
           if (!source) {
             if (error === "FileNotFound") {
@@ -494,10 +542,16 @@ export function expectBundled(
         .filter(Boolean) as any[];
 
       if (allErrors.length === 0) {
-        console.log(stderr!.toString("utf-8"));
+        console.log(errorText);
       }
 
-      if (stderr!.toString("utf-8").includes("Crash report saved to:")) {
+      if (
+        errorText.includes("Crash report saved to:") ||
+        errorText.includes("panic: reached unreachable code") ||
+        errorText.includes("Panic: reached unreachable code") ||
+        errorText.includes("Segmentation fault") ||
+        errorText.includes("bun has crashed")
+      ) {
         throw new Error("Bun crashed during build");
       }
 
@@ -639,6 +693,15 @@ export function expectBundled(
     },
     warnings: warningReference,
     options: opts,
+    captureFile: (file, fnName = "capture") => {
+      const fileContents = readFile(file);
+      const regex = new RegExp(`\\b${fnName}\\s*\\(((?:\\(\\))?.*?)\\)`, "g");
+      const matches = [...fileContents.matchAll(regex)];
+      if (matches.length === 0) {
+        throw new Error(`No ${fnName} calls found in ${file}`);
+      }
+      return matches.map(match => match[1]);
+    },
   } satisfies BundlerTestBundleAPI;
 
   // DCE keep scan
@@ -750,6 +813,11 @@ export function expectBundled(
     }
   }
 
+  if (capture) {
+    const captures = api.captureFile(path.relative(root, outfile ?? outputPaths[0]));
+    expect(captures).toEqual(capture);
+  }
+
   // Write runtime files to disk as well as run the post bundle hook.
   for (const [file, contents] of Object.entries(runtimeFiles ?? {})) {
     mkdirSync(path.dirname(path.join(root, file)), { recursive: true });
@@ -907,7 +975,22 @@ export function itBundled(id: string, opts: BundlerTestInput): BundlerTestRef {
     }
   }
 
-  it(id, () => expectBundled(id, opts));
+  if (LOOSE) {
+    try {
+      expectBundled(id, opts);
+      it(id, () => {});
+    } catch (error: any) {
+      if (error.message === "Bun crashed during build") {
+        it(id, () => {
+          throw error;
+        });
+      } else {
+        it.skip(id, () => {});
+      }
+    }
+  } else {
+    it(id, () => expectBundled(id, opts));
+  }
   return ref;
 }
 itBundled.skip = (id: string, opts: BundlerTestInput) => {
diff --git a/test/bundler/report-bundler-test-progress.sh b/test/bundler/report-bundler-test-progress.sh
index 1ee0fec66..7c0266c59 100644
--- a/test/bundler/report-bundler-test-progress.sh
+++ b/test/bundler/report-bundler-test-progress.sh
@@ -12,7 +12,7 @@ total_skip=0
 
 for test in $tests; do
   defined=$(grep "^import" $test -v | grep -v expectBundled.md | grep -Ec "expectBundled|itBundled")
-  output=$(bun test $test 2>&1 | tail -n 5)
+  output=$(BUN_BUNDLER_TEST_LOOSE=false bun test $test 2>&1 | tail -n 5)
   pass=$(echo "$output" | grep "pass" | cut -d " " -f 2)
   fail=$(echo "$output" | grep "fail" | cut -d " " -f 2)
   skip=$(echo "$output" | grep "skip" | cut -d " " -f 2)
diff --git a/test/bundler/run-single-bundler-test.sh b/test/bundler/run-single-bundler-test.sh
index 0b3cf96b2..a22aee77d 100755
--- a/test/bundler/run-single-bundler-test.sh
+++ b/test/bundler/run-single-bundler-test.sh
@@ -6,6 +6,10 @@ if [ -z "$1" ]; then
   exit 1
 fi
 
+if [ -z "$BUN_EXE"]; then
+  BUN_EXE=$(which bd 2>/dev/null || which bun 2>/dev/null)
+fi
+
 __dirname="$(dirname $(realpath "$0"))"
 cd "$__dirname"