test(@angular/build): verify coverage ignore comments are preserved during compilation

The underlying Vitest coverage engine depends on specific developer comments like `/* istanbul ignore next */` or `/* v8 ignore next */` being present in the executing code to accurately isolate unmeasured blocks.

This commit adds strict behavioral tests to assert that the Angular CLI's in-memory compilation pipeline (via esbuild) properly preserves these structural comments and forwards them reliably to Vitest's coverage processing engine.

Author: clydin

packages/angular/build/src/builders/unit-test/tests/behavior/coverage-ignore-comments_spec.ts

@@ -0,0 +1,143 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { execute } from '../../index';
+import {
+  BASE_OPTIONS,
+  describeBuilder,
+  UNIT_TEST_BUILDER_INFO,
+  setupApplicationTarget,
+} from '../setup';
+
+describeBuilder(execute, UNIT_TEST_BUILDER_INFO, (harness) => {
+  describe('Behavior: "coverage ignore comments"', () => {
+    beforeEach(async () => {
+      setupApplicationTarget(harness);
+    });
+
+    it('should respect istanbul ignore next comments when computing coverage', async () => {
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        coverage: true,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        coverageReporters: ['json'] as any,
+      });
+
+      harness.writeFile(
+        'src/app/app.component.ts',
+        `
+        import { Component } from '@angular/core';
+
+        @Component({
+          selector: 'app-root',
+          template: '<h1>hello</h1>',
+          standalone: true,
+        })
+        export class AppComponent {
+          title = 'app';
+          
+          /* istanbul ignore next */
+          untestedFunction() {
+            return false;
+          }
+        }
+        `,
+      );
+
+      harness.writeFile(
+        'src/app/app.component.spec.ts',
+        `
+        import { AppComponent } from './app.component';
+
+        describe('AppComponent', () => {
+          it('should create', () => {
+            const comp = new AppComponent();
+            expect(comp).toBeTruthy();
+          });
+        });
+        `,
+      );
+
+      const { result } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+      harness.expectFile('coverage/test/coverage-final.json').toExist();
+
+      const coverageMap = JSON.parse(harness.readFile('coverage/test/coverage-final.json'));
+      const appComponentPath = Object.keys(coverageMap).find((p) => p.includes('app.component.ts'));
+      expect(appComponentPath).toBeDefined();
+
+      const appComponentCoverage = coverageMap[appComponentPath!];
+
+      const statementCounts = Object.values(appComponentCoverage.s) as number[];
+      const hasUncoveredStatements = statementCounts.some((count) => count === 0);
+      expect(hasUncoveredStatements)
+        .withContext('There should be no uncovered statements as the uncalled function was ignored')
+        .toBeFalse();
+    });
+
+    it('should respect v8 ignore next comments when computing coverage', async () => {
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        coverage: true,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        coverageReporters: ['json'] as any,
+      });
+
+      harness.writeFile(
+        'src/app/app.component.ts',
+        `
+        import { Component } from '@angular/core';
+
+        @Component({
+          selector: 'app-root',
+          template: '<h1>hello</h1>',
+          standalone: true,
+        })
+        export class AppComponent {
+          title = 'app';
+          
+          /* v8 ignore next */
+          untestedFunction() {
+            return false;
+          }
+        }
+        `,
+      );
+
+      harness.writeFile(
+        'src/app/app.component.spec.ts',
+        `
+        import { AppComponent } from './app.component';
+
+        describe('AppComponent', () => {
+          it('should create', () => {
+            const comp = new AppComponent();
+            expect(comp).toBeTruthy();
+          });
+        });
+        `,
+      );
+
+      const { result } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+      harness.expectFile('coverage/test/coverage-final.json').toExist();
+
+      const coverageMap = JSON.parse(harness.readFile('coverage/test/coverage-final.json'));
+      const appComponentPath = Object.keys(coverageMap).find((p) => p.includes('app.component.ts'));
+      expect(appComponentPath).toBeDefined();
+
+      const appComponentCoverage = coverageMap[appComponentPath!];
+
+      const statementCounts = Object.values(appComponentCoverage.s) as number[];
+      const hasUncoveredStatements = statementCounts.some((count) => count === 0);
+      expect(hasUncoveredStatements)
+        .withContext('There should be no uncovered statements as the uncalled function was ignored')
+        .toBeFalse();
+    });
+  });
+});