test: add web quality gates

src/test/testHarness.ts

@@ -0,0 +1,150 @@
+type TestFn = () => unknown | Promise<unknown>;
+
+interface TestCase {
+  name: string;
+  run: TestFn;
+  afterEachFns: TestFn[];
+}
+
+const tests: TestCase[] = [];
+const suiteStack: string[] = [];
+const afterEachStack: TestFn[][] = [[]];
+
+function formatValue(value: unknown): string {
+  return typeof value === "string" ? `"${value}"` : JSON.stringify(value);
+}
+
+function fail(message: string): never {
+  throw new Error(message);
+}
+
+function assertThrows(
+  actual: unknown,
+  expectedMessage?: string,
+  inverted = false,
+): void {
+  if (typeof actual !== "function") {
+    fail("Expected value to be a function");
+  }
+
+  let thrown: unknown;
+  try {
+    actual();
+  } catch (error) {
+    thrown = error;
+  }
+
+  if (inverted) {
+    if (thrown)
+      fail(
+        `Expected function not to throw, but it threw ${thrown instanceof Error ? thrown.message : String(thrown)}`,
+      );
+    return;
+  }
+
+  if (!thrown) fail("Expected function to throw");
+  if (expectedMessage) {
+    const message = thrown instanceof Error ? thrown.message : String(thrown);
+    if (!message.includes(expectedMessage)) {
+      fail(
+        `Expected thrown message to include "${expectedMessage}", got "${message}"`,
+      );
+    }
+  }
+}
+
+export function describe(name: string, run: () => void): void {
+  suiteStack.push(name);
+  afterEachStack.push([]);
+  try {
+    run();
+  } finally {
+    afterEachStack.pop();
+    suiteStack.pop();
+  }
+}
+
+export function it(name: string, run: TestFn): void {
+  tests.push({
+    name: [...suiteStack, name].join(" > "),
+    run,
+    afterEachFns: afterEachStack.flat(),
+  });
+}
+
+export function afterEach(run: TestFn): void {
+  afterEachStack[afterEachStack.length - 1].push(run);
+}
+
+export function expect(actual: unknown) {
+  return {
+    toBe(expected: unknown): void {
+      if (!Object.is(actual, expected)) {
+        fail(`Expected ${formatValue(actual)} to be ${formatValue(expected)}`);
+      }
+    },
+    toEqual(expected: unknown): void {
+      const actualJson = JSON.stringify(actual);
+      const expectedJson = JSON.stringify(expected);
+      if (actualJson !== expectedJson) {
+        fail(`Expected ${actualJson} to equal ${expectedJson}`);
+      }
+    },
+    toThrow(expectedMessage?: string): void {
+      assertThrows(actual, expectedMessage);
+    },
+    not: {
+      toThrow(): void {
+        assertThrows(actual, undefined, true);
+      },
+    },
+  };
+}
+
+export async function runRegisteredTests(): Promise<{
+  passed: number;
+  failed: number;
+  total: number;
+}> {
+  let passed = 0;
+  let failed = 0;
+
+  for (const test of tests) {
+    let failure: unknown;
+    try {
+      await test.run();
+    } catch (error) {
+      failure = error;
+    }
+
+    for (const hook of [...test.afterEachFns].reverse()) {
+      try {
+        await hook();
+      } catch (error) {
+        failure = failure || error;
+      }
+    }
+
+    if (failure) {
+      failed += 1;
+      console.error(`FAIL ${test.name}`);
+      console.error(
+        failure instanceof Error
+          ? `  ${failure.message}`
+          : `  ${String(failure)}`,
+      );
+    } else {
+      passed += 1;
+      console.log(`PASS ${test.name}`);
+    }
+  }
+
+  const total = passed + failed;
+  if (total === 0) {
+    console.error("No unit tests were registered.");
+    return { passed, failed: 1, total };
+  }
+
+  console.log(`\n${passed} passed, ${failed} failed`);
+  return { passed, failed, total };
+}