Function assertOnly

testing/bdd_test.ts:1345–1389

* Asserts that when only is used on a nested `describe` or `it` call, it will be the only test case or suite that runs in the file. * This is used to reduce code duplication when testing calling `describe.ignore` with different call signatures.

(
      cb: (fns: readonly [Spy, Spy, Spy]) => void,
    )

     * This is used to reduce code duplication when testing calling `describe.ignore` with different call signatures.
     */
    async function assertOnly(
      cb: (fns: readonly [Spy, Spy, Spy]) => void,
    ) {
      using test = stub(Deno, "test");
      const fns = [spy(), spy(), spy()] as const;
      try {
        cb(fns);

        assertSpyCall(test, 0);
        const call = test.calls[0];
        const options = call?.args[0] as Deno.TestDefinition;
        assertEquals(
          Object.keys(options).sort(),
          ["name", "only", "fn"].sort(),
        );
        assertObjectMatch(options, {
          name: "example",
          only: true,
        });

        assertSpyCalls(fns[0], 0);
        assertSpyCalls(fns[1], 0);

        const context = new TestContext("example");
        const result = options.fn(context);
        assertStrictEquals(Promise.resolve(result), result);
        assertEquals(await result, undefined);
        assertSpyCalls(context.spies.step, 1);

        let fn = fns[0];
        assertSpyCalls(fn, 0);

        fn = fns[1];
        assertSpyCall(fn, 0, {
          self: {},
          returned: undefined,
        });
        assertSpyCalls(fn, 1);

        fn = fns[2];
        assertSpyCalls(fn, 0);
      } finally {
        TestSuiteInternal.reset();
      }
    }

    await t.step("it", async () =>
      await assertOnly((fns) => {