Improve types for `test.each`, `describe.each` (#5838)

* Improve types for each

* more

* remove

2 files changed, 59 insertions, 10 deletions

diff --git a/packages/bun-types/bun-test.d.ts b/packages/bun-types/bun-test.d.ts
index b32ffb4f7..6c22ad62f 100644
--- a/packages/bun-types/bun-test.d.ts
+++ b/packages/bun-types/bun-test.d.ts
@@ -174,18 +174,18 @@ declare module "bun:test" {
      *
      * @param table Array of Arrays with the arguments that are passed into the test fn for each row.
      */
-    each<T extends ReadonlyArray<unknown>>(
-      table: ReadonlyArray<T>,
+    each<T extends Readonly<Readonly<[any, ...any[]]>[]>>(
+      table: T,
     ): (
       label: string,
-      fn: (...args: T) => void | Promise<unknown>,
+      fn: (...args: Readonly<T>[number]) => void | Promise<unknown>,
       options?: number | TestOptions,
     ) => void;
-    each<T>(
+    each<T extends Array<any>>(
       table: ReadonlyArray<T>,
     ): (
       label: string,
-      fn: (arg: T) => void | Promise<unknown>,
+      fn: (...args: Readonly<T>) => void | Promise<unknown>,
       options?: number | TestOptions,
     ) => void;
   };
@@ -419,18 +419,18 @@ declare module "bun:test" {
      *
      * @param table Array of Arrays with the arguments that are passed into the test fn for each row.
      */
-    each<T extends ReadonlyArray<unknown>>(
-      table: ReadonlyArray<T>,
+    each<T extends Readonly<Readonly<[any, ...any[]]>[]>>(
+      table: T,
     ): (
       label: string,
-      fn: (...args: T) => void | Promise<unknown>,
+      fn: (...args: Readonly<T>[number]) => void | Promise<unknown>,
       options?: number | TestOptions,
     ) => void;
-    each<T>(
+    each<T extends Array<any>>(
       table: ReadonlyArray<T>,
     ): (
       label: string,
-      fn: (arg: T, done: (err?: unknown) => void) => void | Promise<unknown>,
+      fn: (...args: Readonly<T>) => void | Promise<unknown>,
       options?: number | TestOptions,
     ) => void;
   };
diff --git a/packages/bun-types/tests/test.test-d.ts b/packages/bun-types/tests/test.test-d.ts
index 831b18e2e..1e67590b2 100644
--- a/packages/bun-types/tests/test.test-d.ts
+++ b/packages/bun-types/tests/test.test-d.ts
@@ -63,3 +63,52 @@ describe("bun:test", () => {
     expect(undefined).not.toBeDefined();
   });
 });
+
+// inference should work when data is passed directly in
+test.each([
+  ["a", true, 5],
+  ["b", false, 1234],
+])("test.each", (a, b, c) => {
+  expectType<string>(a);
+  expectType<boolean>(b);
+  expectType<number | string>(c);
+});
+describe.each([
+  ["a", true, 5],
+  ["b", false, "asdf"],
+])("test.each", (a, b, c) => {
+  expectType<string>(a);
+  expectType<boolean>(b);
+  expectType<number | string>(c);
+});
+
+// no inference on data
+const data = [
+  ["a", true, 5],
+  ["b", false, "asdf"],
+];
+test.each(data)("test.each", (...args) => {
+  expectType<string | number | boolean>(args[0]);
+});
+describe.each(data)("test.each", (a, b, c) => {
+  expectType<string | number | boolean>(a);
+  expectType<string | number | boolean>(b);
+  expectType<string | number | boolean>(c);
+});
+
+// as const
+const dataAsConst = [
+  ["a", true, 5],
+  ["b", false, "asdf"],
+] as const;
+
+test.each(dataAsConst)("test.each", (...args) => {
+  expectType<string>(args[0]);
+  expectType<boolean>(args[1]);
+  expectType<string | number>(args[2]);
+});
+describe.each(dataAsConst)("test.each", (...args) => {
+  expectType<string>(args[0]);
+  expectType<boolean>(args[1]);
+  expectType<string | number>(args[2]);
+});