diff --git a/packages/schematics/angular/migrations/migration-collection.json b/packages/schematics/angular/migrations/migration-collection.json
index d402927d5f6b..40ec225245ed 100644
--- a/packages/schematics/angular/migrations/migration-collection.json
+++ b/packages/schematics/angular/migrations/migration-collection.json
@@ -19,6 +19,11 @@
       "version": "15.0.0",
       "factory": "./update-15/update-workspace-config",
       "description": "Remove options from 'angular.json' that are no longer supported by the official builders."
+    },
+    "update-karma-main-file": {
+      "version": "15.0.0",
+      "factory": "./update-15/update-karma-main-file",
+      "description": "Remove no longer needed require calls in Karma builder main file."
     }
   }
 }
diff --git a/packages/schematics/angular/migrations/update-15/update-karma-main-file.ts b/packages/schematics/angular/migrations/update-15/update-karma-main-file.ts
new file mode 100644
index 000000000000..0a7e08ba10f1
--- /dev/null
+++ b/packages/schematics/angular/migrations/update-15/update-karma-main-file.ts
@@ -0,0 +1,101 @@
+/**
+ * @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.io/license
+ */
+
+import { Rule, Tree } from '@angular-devkit/schematics';
+import * as ts from '../../third_party/github.com/Microsoft/TypeScript/lib/typescript';
+import { readWorkspace } from '../../utility';
+import { allTargetOptions } from '../../utility/workspace';
+import { Builders } from '../../utility/workspace-models';
+
+export default function (): Rule {
+  return async (host) => {
+    for (const file of await findTestMainFiles(host)) {
+      updateTestFile(host, file);
+    }
+  };
+}
+
+async function findTestMainFiles(host: Tree): Promise<Set<string>> {
+  const testFiles = new Set<string>();
+  const workspace = await readWorkspace(host);
+
+  // find all test.ts files.
+  for (const project of workspace.projects.values()) {
+    for (const target of project.targets.values()) {
+      if (target.builder !== Builders.Karma) {
+        continue;
+      }
+
+      for (const [, options] of allTargetOptions(target)) {
+        if (typeof options.main === 'string') {
+          testFiles.add(options.main);
+        }
+      }
+    }
+  }
+
+  return testFiles;
+}
+
+function updateTestFile(host: Tree, file: string): void {
+  const content = host.readText(file);
+  if (!content.includes('require.context')) {
+    return;
+  }
+
+  const sourceFile = ts.createSourceFile(
+    file,
+    content.replace(/^\uFEFF/, ''),
+    ts.ScriptTarget.Latest,
+    true,
+  );
+
+  const usedVariableNames = new Set<string>();
+  const recorder = host.beginUpdate(sourceFile.fileName);
+
+  ts.forEachChild(sourceFile, (node) => {
+    if (ts.isVariableStatement(node)) {
+      const variableDeclaration = node.declarationList.declarations[0];
+
+      if (ts.getModifiers(node)?.some((m) => m.kind === ts.SyntaxKind.DeclareKeyword)) {
+        // `declare const require`
+        if (variableDeclaration.name.getText() !== 'require') {
+          return;
+        }
+      } else {
+        // `const context = require.context('./', true, /\.spec\.ts$/);`
+        if (!variableDeclaration.initializer?.getText().startsWith('require.context')) {
+          return;
+        }
+
+        // add variable name as used.
+        usedVariableNames.add(variableDeclaration.name.getText());
+      }
+
+      // Delete node.
+      recorder.remove(node.getFullStart(), node.getFullWidth());
+    }
+
+    if (
+      usedVariableNames.size &&
+      ts.isExpressionStatement(node) && // context.keys().map(context);
+      ts.isCallExpression(node.expression) && // context.keys().map(context);
+      ts.isPropertyAccessExpression(node.expression.expression) && // context.keys().map
+      ts.isCallExpression(node.expression.expression.expression) && // context.keys()
+      ts.isPropertyAccessExpression(node.expression.expression.expression.expression) && // context.keys
+      ts.isIdentifier(node.expression.expression.expression.expression.expression) && // context
+      usedVariableNames.has(node.expression.expression.expression.expression.expression.getText())
+    ) {
+      // `context.keys().map(context);`
+      // `context.keys().forEach(context);`
+      recorder.remove(node.getFullStart(), node.getFullWidth());
+    }
+  });
+
+  host.commitUpdate(recorder);
+}
diff --git a/packages/schematics/angular/migrations/update-15/update-karma-main-file_spec.ts b/packages/schematics/angular/migrations/update-15/update-karma-main-file_spec.ts
new file mode 100644
index 000000000000..d8da17b2a1c6
--- /dev/null
+++ b/packages/schematics/angular/migrations/update-15/update-karma-main-file_spec.ts
@@ -0,0 +1,151 @@
+/**
+ * @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.io/license
+ */
+
+import { tags } from '@angular-devkit/core';
+import { EmptyTree } from '@angular-devkit/schematics';
+import { SchematicTestRunner, UnitTestTree } from '@angular-devkit/schematics/testing';
+import { Builders, ProjectType, WorkspaceSchema } from '../../utility/workspace-models';
+
+function createWorkspace(tree: UnitTestTree): void {
+  const angularConfig: WorkspaceSchema = {
+    version: 1,
+    projects: {
+      app: {
+        root: '',
+        sourceRoot: 'src',
+        projectType: ProjectType.Application,
+        prefix: 'app',
+        architect: {
+          test: {
+            builder: Builders.Karma,
+            options: {
+              main: 'test.ts',
+              karmaConfig: './karma.config.js',
+              tsConfig: 'test-spec.json',
+            },
+            configurations: {
+              production: {
+                main: 'test-multiple-context.ts',
+              },
+            },
+          },
+        },
+      },
+    },
+  };
+
+  tree.create('/angular.json', JSON.stringify(angularConfig, undefined, 2));
+  tree.create(
+    'test.ts',
+    tags.stripIndents`
+  import { getTestBed } from '@angular/core/testing';
+  import {
+    BrowserDynamicTestingModule,
+    platformBrowserDynamicTesting
+  } from '@angular/platform-browser-dynamic/testing';
+
+  declare const require: {
+    context(path: string, deep?: boolean, filter?: RegExp): {
+      <T>(id: string): T;
+      keys(): string[];
+    };
+  };
+
+  // First, initialize the Angular testing environment.
+  getTestBed().initTestEnvironment(
+    BrowserDynamicTestingModule,
+    platformBrowserDynamicTesting(),
+  );
+
+  // Then we find all the tests.
+  const context = require.context('./', true, /\.spec\.ts$/);
+  // And load the modules.
+  context.keys().map(context);
+  `,
+  );
+
+  tree.create(
+    'test-multiple-context.ts',
+    tags.stripIndents`
+  import { getTestBed } from '@angular/core/testing';
+  import {
+    BrowserDynamicTestingModule,
+    platformBrowserDynamicTesting
+  } from '@angular/platform-browser-dynamic/testing';
+
+  declare const require: {
+    context(path: string, deep?: boolean, filter?: RegExp): {
+      <T>(id: string): T;
+      keys(): string[];
+    };
+  };
+
+  // First, initialize the Angular testing environment.
+  getTestBed().initTestEnvironment(
+    BrowserDynamicTestingModule,
+    platformBrowserDynamicTesting(),
+  );
+
+  // Then we find all the tests.
+  const context1 = require.context('./', true, /\.spec\.ts$/);
+  const context2 = require.context('./', true, /\.spec\.ts$/);
+  // And load the modules.
+  context2.keys().forEach(context2);
+  context1.keys().map(context1);
+  `,
+  );
+}
+
+describe(`Migration to karma builder main file (test.ts)`, () => {
+  const schematicName = 'update-karma-main-file';
+
+  const schematicRunner = new SchematicTestRunner(
+    'migrations',
+    require.resolve('../migration-collection.json'),
+  );
+
+  let tree: UnitTestTree;
+  beforeEach(() => {
+    tree = new UnitTestTree(new EmptyTree());
+    createWorkspace(tree);
+  });
+
+  it(`should remove 'declare const require' and 'require.context' usages`, async () => {
+    const newTree = await schematicRunner.runSchematicAsync(schematicName, {}, tree).toPromise();
+    expect(newTree.readText('test.ts')).toBe(tags.stripIndents`
+      import { getTestBed } from '@angular/core/testing';
+      import {
+        BrowserDynamicTestingModule,
+        platformBrowserDynamicTesting
+      } from '@angular/platform-browser-dynamic/testing';
+
+      // First, initialize the Angular testing environment.
+      getTestBed().initTestEnvironment(
+        BrowserDynamicTestingModule,
+        platformBrowserDynamicTesting(),
+      );
+    `);
+  });
+
+  it(`should remove multiple 'require.context' usages`, async () => {
+    const newTree = await schematicRunner.runSchematicAsync(schematicName, {}, tree).toPromise();
+    expect(newTree.readText('test-multiple-context.ts')).toBe(tags.stripIndents`
+      import { getTestBed } from '@angular/core/testing';
+      import {
+        BrowserDynamicTestingModule,
+        platformBrowserDynamicTesting
+      } from '@angular/platform-browser-dynamic/testing';
+
+      // First, initialize the Angular testing environment.
+      getTestBed().initTestEnvironment(
+        BrowserDynamicTestingModule,
+        platformBrowserDynamicTesting(),
+      );
+    `);
+  });
+});