Fix discovery and execution of root-level tests in the parallel runner (#32980)

Author: weswigham

src/testRunner/parallel/host.ts

@@ -626,6 +626,7 @@ namespace Harness.Parallel.Host {
 
             const perfData = readSavedPerfData(configOption);
             context.describe = addSuite as Mocha.SuiteFunction;
+            context.it = addSuite as Mocha.TestFunction;
 
             function addSuite(title: string) {
                 // Note, sub-suites are not indexed (we assume such granularity is not required)

src/testRunner/parallel/worker.ts

@@ -151,24 +151,42 @@ namespace Harness.Parallel.Worker {
                     unitTestSuiteMap.set(suite.title, suite);
                 }
             }
+            if (!unitTestTestMap && unitTestSuite.tests.length) {
+                unitTestTestMap = ts.createMap<Mocha.Test>();
+                for (const test of unitTestSuite.tests) {
+                    unitTestTestMap.set(test.title, test);
+                }
+            }
 
-            if (!unitTestSuiteMap) {
+            if (!unitTestSuiteMap && !unitTestTestMap) {
                 throw new Error(`Asked to run unit test ${task.file}, but no unit tests were discovered!`);
             }
 
-            const suite = unitTestSuiteMap.get(task.file);
-            if (!suite) {
+            let suite = unitTestSuiteMap.get(task.file);
+            const test = unitTestTestMap.get(task.file);
+            if (!suite && !test) {
                 throw new Error(`Unit test with name "${task.file}" was asked to be run, but such a test does not exist!`);
             }
 
             const root = new Suite("", new Mocha.Context());
             root.timeout(globalTimeout || 40_000);
-            root.addSuite(suite);
-            Object.setPrototypeOf(suite.ctx, root.ctx);
+            if (suite) {
+                root.addSuite(suite);
+                Object.setPrototypeOf(suite.ctx, root.ctx);
+            }
+            else if (test) {
+                const newSuite = new Suite("", new Mocha.Context());
+                newSuite.addTest(test);
+                root.addSuite(newSuite);
+                Object.setPrototypeOf(newSuite.ctx, root.ctx);
+                Object.setPrototypeOf(test.ctx, root.ctx);
+                test.parent = newSuite;
+                suite = newSuite;
+            }
 
-            runSuite(task, suite, payload => {
-                suite.parent = unitTestSuite;
-                Object.setPrototypeOf(suite.ctx, unitTestSuite.ctx);
+            runSuite(task, suite!, payload => {
+                suite!.parent = unitTestSuite;
+                Object.setPrototypeOf(suite!.ctx, unitTestSuite.ctx);
                 fn(payload);
             });
         }
@@ -284,6 +302,8 @@ namespace Harness.Parallel.Worker {
         // The root suite for all unit tests.
         let unitTestSuite: Suite;
         let unitTestSuiteMap: ts.Map<Mocha.Suite>;
+        // (Unit) Tests directly within the root suite
+        let unitTestTestMap: ts.Map<Mocha.Test>;
 
         if (runUnitTests) {
             unitTestSuite = new Suite("", new Mocha.Context());

tests/baselines/reference/tsbuild/moduleSpecifiers/initial-build/resolves-correctly.js

@@ -14,8 +14,8 @@ exports.__esModule = true;
   "program": {
     "fileInfos": {
       "../../../.ts/lib.es5.d.ts": {
-        "version": "146944634190",
-        "signature": "146944634190"
+        "version": "406734842058",
+        "signature": "406734842058"
       },
       "../../../.ts/lib.es2015.d.ts": {
         "version": "57263133672",
@@ -114,8 +114,8 @@ exports.__esModule = true;
   "program": {
     "fileInfos": {
       "../../../.ts/lib.es5.d.ts": {
-        "version": "146944634190",
-        "signature": "146944634190"
+        "version": "406734842058",
+        "signature": "406734842058"
       },
       "../../../.ts/lib.es2015.d.ts": {
         "version": "57263133672",
@@ -237,8 +237,8 @@ exports.getVar = getVar;
   "program": {
     "fileInfos": {
       "../../../.ts/lib.es5.d.ts": {
-        "version": "146944634190",
-        "signature": "146944634190"
+        "version": "406734842058",
+        "signature": "406734842058"
       },
       "../../../.ts/lib.es2015.d.ts": {
         "version": "57263133672",