test(@angular/build): add test harness rebuild case helper function

To reduce duplicate code within tests for rebuild/watch scenarios, a new
helper has been added to the builder test harness.  This helper allows
passing in an array of test case functions that are executed in order per
rebuild. The development server's watch option tests have been updated to
use the new helper.

Author: clydin

modules/testing/builder/src/jasmine-helpers.ts

@@ -9,9 +9,16 @@
 import { BuilderHandlerFn } from '@angular-devkit/architect';
 import { json } from '@angular-devkit/core';
 import { readFileSync } from 'fs';
-import { BuilderHarness } from './builder-harness';
+import { concatMap, count, firstValueFrom, take, timeout } from 'rxjs';
+import { BuilderHarness, BuilderHarnessExecutionResult } from './builder-harness';
 import { host } from './test-utils';
 
+/**
+ * Maximum time for single build/rebuild
+ * This accounts for CI variability.
+ */
+export const BUILD_TIMEOUT = 25_000;
+
 const optionSchemaCache = new Map<string, json.schema.JsonSchema>();
 
 export function describeBuilder<T>(
@@ -45,6 +52,24 @@ export class JasmineBuilderHarness<T> extends BuilderHarness<T> {
   expectDirectory(path: string): HarnessDirectoryMatchers {
     return expectDirectory(path, this);
   }
+
+  async executeWithCases(
+    cases: ((
+      executionResult: BuilderHarnessExecutionResult,
+      index: number,
+    ) => void | Promise<void>)[],
+  ): Promise<void> {
+    const executionCount = await firstValueFrom(
+      this.execute().pipe(
+        timeout(BUILD_TIMEOUT),
+        concatMap(async (result, index) => await cases[index](result, index)),
+        take(cases.length),
+        count(),
+      ),
+    );
+
+    expect(executionCount).toBe(cases.length);
+  }
 }
 
 export interface HarnessFileMatchers {

packages/angular/build/src/builders/dev-server/tests/options/watch_spec.ts

@@ -6,10 +6,10 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { TimeoutError, concatMap, count, take, timeout } from 'rxjs';
+import { TimeoutError } from 'rxjs';
 import { executeDevServer } from '../../index';
 import { describeServeBuilder } from '../jasmine-helpers';
-import { BASE_OPTIONS, BUILD_TIMEOUT, DEV_SERVER_BUILDER_INFO } from '../setup';
+import { BASE_OPTIONS, DEV_SERVER_BUILDER_INFO } from '../setup';
 
 describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupTarget) => {
   describe('Option: "watch"', () => {
@@ -24,27 +24,21 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
       });
 
       await harness
-        .execute()
-        .pipe(
-          timeout(BUILD_TIMEOUT),
-          concatMap(async ({ result }, index) => {
+        .executeWithCases([
+          async ({ result }) => {
+            // Initial build should succeed
             expect(result?.success).toBe(true);
 
-            switch (index) {
-              case 0:
-                await harness.modifyFile(
-                  'src/main.ts',
-                  (content) => content + 'console.log("abcd1234");',
-                );
-                break;
-              case 1:
-                fail('Expected files to not be watched.');
-                break;
-            }
-          }),
-          take(2),
-        )
-        .toPromise()
+            // Modify a file to attempt to trigger file watcher
+            await harness.modifyFile(
+              'src/main.ts',
+              (content) => content + 'console.log("abcd1234");',
+            );
+          },
+          () => {
+            fail('Expected files to not be watched.');
+          },
+        ])
         .catch((error) => {
           // Timeout is expected if watching is disabled
           if (error instanceof TimeoutError) {
@@ -60,30 +54,22 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
         watch: undefined,
       });
 
-      const buildCount = await harness
-        .execute()
-        .pipe(
-          timeout(BUILD_TIMEOUT),
-          concatMap(async ({ result }, index) => {
-            expect(result?.success).toBe(true);
-
-            switch (index) {
-              case 0:
-                await harness.modifyFile(
-                  'src/main.ts',
-                  (content) => content + 'console.log("abcd1234");',
-                );
-                break;
-              case 1:
-                break;
-            }
-          }),
-          take(2),
-          count(),
-        )
-        .toPromise();
+      await harness.executeWithCases([
+        async ({ result }) => {
+          // Initial build should succeed
+          expect(result?.success).toBe(true);
 
-      expect(buildCount).toBe(2);
+          // Modify a file to trigger file watcher
+          await harness.modifyFile(
+            'src/main.ts',
+            (content) => content + 'console.log("abcd1234");',
+          );
+        },
+        async ({ result }) => {
+          // Modifying a file should trigger a successful rebuild
+          expect(result?.success).toBe(true);
+        },
+      ]);
     });
 
     it('watches for file changes when true', async () => {
@@ -92,30 +78,22 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
         watch: true,
       });
 
-      const buildCount = await harness
-        .execute()
-        .pipe(
-          timeout(BUILD_TIMEOUT),
-          concatMap(async ({ result }, index) => {
-            expect(result?.success).toBe(true);
-
-            switch (index) {
-              case 0:
-                await harness.modifyFile(
-                  'src/main.ts',
-                  (content) => content + 'console.log("abcd1234");',
-                );
-                break;
-              case 1:
-                break;
-            }
-          }),
-          take(2),
-          count(),
-        )
-        .toPromise();
+      await harness.executeWithCases([
+        async ({ result }) => {
+          // Initial build should succeed
+          expect(result?.success).toBe(true);
 
-      expect(buildCount).toBe(2);
+          // Modify a file to trigger file watcher
+          await harness.modifyFile(
+            'src/main.ts',
+            (content) => content + 'console.log("abcd1234");',
+          );
+        },
+        async ({ result }) => {
+          // Modifying a file should trigger a successful rebuild
+          expect(result?.success).toBe(true);
+        },
+      ]);
     });
   });
 });