4 files changed, 153 insertions, 2 deletions
diff --git a/test/js/bun/io/bun-write-exdev-fixture.js b/test/js/bun/io/bun-write-exdev-fixture.js
new file mode 100644
index 000000000..81cd263e3
--- /dev/null
+++ b/test/js/bun/io/bun-write-exdev-fixture.js
@@ -0,0 +1 @@
+await Bun.write(Bun.file(process.argv.at(-1)), Bun.file(process.argv.at(-2)));
diff --git a/test/js/bun/io/bun-write.test.js b/test/js/bun/io/bun-write.test.js
index 120ba396d..b67df9405 100644
--- a/test/js/bun/io/bun-write.test.js
+++ b/test/js/bun/io/bun-write.test.js
@@ -1,6 +1,6 @@
-import fs from "fs";
+import fs, { mkdirSync } from "fs";
 import { it, expect, describe } from "bun:test";
-import path from "path";
+import path, { join } from "path";
 import { gcTick, withoutAggressiveGC, bunExe, bunEnv } from "harness";
 import { tmpdir } from "os";
 
@@ -307,3 +307,77 @@ it("#2674", async () => {
   expect(error?.length).toBeFalsy();
   expect(exitCode).toBe(0);
 });
+
+if (process.platform === "linux") {
+  describe("should work when copyFileRange is not available", () => {
+    it("on large files", () => {
+      var tempdir = `${tmpdir()}/fs.test.js/${Date.now()}-1/bun-write/large`;
+      expect(fs.existsSync(tempdir)).toBe(false);
+      expect(tempdir.includes(mkdirSync(tempdir, { recursive: true }))).toBe(true);
+      var buffer = new Int32Array(1024 * 1024 * 64);
+      for (let i = 0; i < buffer.length; i++) {
+        buffer[i] = i % 256;
+      }
+
+      const hash = Bun.hash(buffer.buffer);
+      const src = join(tempdir, "Bun.write.src.blob");
+      const dest = join(tempdir, "Bun.write.dest.blob");
+
+      try {
+        fs.writeFileSync(src, buffer.buffer);
+
+        expect(fs.existsSync(dest)).toBe(false);
+
+        const { exitCode } = Bun.spawnSync({
+          stdio: ["inherit", "inherit", "inherit"],
+          cmd: [bunExe(), join(import.meta.dir, "./bun-write-exdev-fixture.js"), src, dest],
+          env: {
+            ...bunEnv,
+            BUN_CONFIG_DISABLE_COPY_FILE_RANGE: "1",
+          },
+        });
+        expect(exitCode).toBe(0);
+
+        expect(Bun.hash(fs.readFileSync(dest))).toBe(hash);
+      } finally {
+        fs.rmSync(src, { force: true });
+        fs.rmSync(dest, { force: true });
+      }
+    });
+
+    it("on small files", () => {
+      const tempdir = `${tmpdir()}/fs.test.js/${Date.now()}-1/bun-write/small`;
+      expect(fs.existsSync(tempdir)).toBe(false);
+      expect(tempdir.includes(mkdirSync(tempdir, { recursive: true }))).toBe(true);
+      var buffer = new Int32Array(1 * 1024);
+      for (let i = 0; i < buffer.length; i++) {
+        buffer[i] = i % 256;
+      }
+
+      const hash = Bun.hash(buffer.buffer);
+      const src = join(tempdir, "Bun.write.src.blob");
+      const dest = join(tempdir, "Bun.write.dest.blob");
+
+      try {
+        fs.writeFileSync(src, buffer.buffer);
+
+        expect(fs.existsSync(dest)).toBe(false);
+
+        const { exitCode } = Bun.spawnSync({
+          stdio: ["inherit", "inherit", "inherit"],
+          cmd: [bunExe(), join(import.meta.dir, "./bun-write-exdev-fixture.js"), src, dest],
+          env: {
+            ...bunEnv,
+            BUN_CONFIG_DISABLE_COPY_FILE_RANGE: "1",
+          },
+        });
+        expect(exitCode).toBe(0);
+
+        expect(Bun.hash(fs.readFileSync(dest))).toBe(hash);
+      } finally {
+        fs.rmSync(src, { force: true });
+        fs.rmSync(dest, { force: true });
+      }
+    });
+  });
+}
diff --git a/test/js/node/fs/fs-fixture-copyFile-no-copy_file_range.js b/test/js/node/fs/fs-fixture-copyFile-no-copy_file_range.js
new file mode 100644
index 000000000..4e990e1c7
--- /dev/null
+++ b/test/js/node/fs/fs-fixture-copyFile-no-copy_file_range.js
@@ -0,0 +1,3 @@
+const { copyFileSync } = require("node:fs");
+
+copyFileSync(process.argv.at(-2), process.argv.at(-1));
diff --git a/test/js/node/fs/fs.test.ts b/test/js/node/fs/fs.test.ts
index 58fb455fc..fac7c2b57 100644
--- a/test/js/node/fs/fs.test.ts
+++ b/test/js/node/fs/fs.test.ts
@@ -134,6 +134,79 @@ describe("copyFileSync", () => {
     copyFileSync(tempdir + "/copyFileSync.src.blob", tempdir + "/copyFileSync.dest.blob");
     expect(Bun.hash(readFileSync(tempdir + "/copyFileSync.dest.blob"))).toBe(Bun.hash(buffer.buffer));
   });
+
+  if (process.platform === "linux") {
+    describe("should work when copyFileRange is not available", () => {
+      it("on large files", () => {
+        const tempdir = `${tmpdir()}/fs.test.js/${Date.now()}-1/1234/large`;
+        expect(existsSync(tempdir)).toBe(false);
+        expect(tempdir.includes(mkdirSync(tempdir, { recursive: true })!)).toBe(true);
+        var buffer = new Int32Array(128 * 1024);
+        for (let i = 0; i < buffer.length; i++) {
+          buffer[i] = i % 256;
+        }
+
+        const hash = Bun.hash(buffer.buffer);
+        const src = tempdir + "/copyFileSync.src.blob";
+        const dest = tempdir + "/copyFileSync.dest.blob";
+
+        writeFileSync(src, buffer.buffer);
+        try {
+          expect(existsSync(dest)).toBe(false);
+
+          const { exitCode } = spawnSync({
+            stdio: ["inherit", "inherit", "inherit"],
+            cmd: [bunExe(), join(import.meta.dir, "./fs-fixture-copyFile-no-copy_file_range.js"), src, dest],
+            env: {
+              ...bunEnv,
+              BUN_CONFIG_DISABLE_COPY_FILE_RANGE: "1",
+            },
+          });
+          expect(exitCode).toBe(0);
+
+          expect(Bun.hash(readFileSync(dest))).toBe(hash);
+        } finally {
+          rmSync(src, { force: true });
+          rmSync(dest, { force: true });
+        }
+      });
+
+      it("on small files", () => {
+        const tempdir = `${tmpdir()}/fs.test.js/${Date.now()}-1/1234/small`;
+        expect(existsSync(tempdir)).toBe(false);
+        expect(tempdir.includes(mkdirSync(tempdir, { recursive: true })!)).toBe(true);
+        var buffer = new Int32Array(1 * 1024);
+        for (let i = 0; i < buffer.length; i++) {
+          buffer[i] = i % 256;
+        }
+
+        const hash = Bun.hash(buffer.buffer);
+        const src = tempdir + "/copyFileSync.src.blob";
+        const dest = tempdir + "/copyFileSync.dest.blob";
+
+        try {
+          writeFileSync(src, buffer.buffer);
+
+          expect(existsSync(dest)).toBe(false);
+
+          const { exitCode } = spawnSync({
+            stdio: ["inherit", "inherit", "inherit"],
+            cmd: [bunExe(), join(import.meta.dir, "./fs-fixture-copyFile-no-copy_file_range.js"), src, dest],
+            env: {
+              ...bunEnv,
+              BUN_CONFIG_DISABLE_COPY_FILE_RANGE: "1",
+            },
+          });
+          expect(exitCode).toBe(0);
+
+          expect(Bun.hash(readFileSync(dest))).toBe(hash);
+        } finally {
+          rmSync(src, { force: true });
+          rmSync(dest, { force: true });
+        }
+      });
+    });
+  }
 });
 
 describe("mkdirSync", () => {