feat(jest-runner): switch mutants using env (#2416)

Pass the active mutant id through the env vars rather than config. This allows the jest transpiler files to be cached.

Co-authored-by: Gareth Parker <gareth.parker@ros.gov.uk>
Co-authored-by: Nico Jansen <jansennico@gmail.com>

packages/jest-runner/src/JestTestRunner.ts

@@ -1,4 +1,4 @@
-import { StrykerOptions, INSTRUMENTER_CONSTANTS, Mutant } from '@stryker-mutator/api/core';
+import { StrykerOptions, INSTRUMENTER_CONSTANTS } from '@stryker-mutator/api/core';
 import { Logger } from '@stryker-mutator/api/logging';
 import { commonTokens, Injector, PluginContext, tokens } from '@stryker-mutator/api/plugin';
 import {
@@ -37,8 +37,6 @@ jestTestRunnerFactory.inject = tokens(commonTokens.injector);
 
 export default class JestTestRunner implements TestRunner2 {
   private readonly jestConfig: jest.Config.InitialOptions;
-  private mutantRunJestConfigCache: jest.Config.InitialOptions | undefined;
-
   private readonly enableFindRelatedTests: boolean;
 
   public static inject = tokens(commonTokens.logger, commonTokens.options, processEnvToken, jestTestAdapterToken, configLoaderToken);
@@ -73,31 +71,18 @@ export default class JestTestRunner implements TestRunner2 {
   }
 
   public dryRun(): Promise<DryRunResult> {
-    return this.run(this.jestConfig);
+    return this.run();
   }
   public async mutantRun({ activeMutant, sandboxFileName }: MutantRunOptions): Promise<MutantRunResult> {
     const fileUnderTest = this.enableFindRelatedTests ? sandboxFileName : undefined;
-    const dryRunResult = await this.run(this.getMutantRunOptions(activeMutant), fileUnderTest);
+    process.env[INSTRUMENTER_CONSTANTS.ACTIVE_MUTANT_ENV_VARIABLE] = activeMutant.id.toString();
+    const dryRunResult = await this.run(fileUnderTest);
     return toMutantRunResult(dryRunResult);
   }
 
-  private getMutantRunOptions(activeMutant: Mutant): jest.Config.InitialOptions {
-    if (!this.mutantRunJestConfigCache) {
-      this.mutantRunJestConfigCache = {
-        ...this.jestConfig,
-        globals: {
-          ...this.jestConfig.globals,
-        },
-      };
-    }
-    this.mutantRunJestConfigCache.globals![INSTRUMENTER_CONSTANTS.ACTIVE_MUTANT] = activeMutant.id;
-    return this.mutantRunJestConfigCache;
-  }
-
-  private async run(config: jest.Config.InitialOptions, fileUnderTest: string | undefined = undefined): Promise<DryRunResult> {
+  private async run(fileUnderTest: string | undefined = undefined): Promise<DryRunResult> {
     this.setEnv();
-    const all = await this.jestTestAdapter.run(config, process.cwd(), fileUnderTest);
-
+    const all = await this.jestTestAdapter.run(this.jestConfig, process.cwd(), fileUnderTest);
     return this.collectRunResult(all.results);
   }
 

packages/jest-runner/test/integration/JestTestRunner.it.spec.ts

@@ -29,7 +29,6 @@ describe(`${JestTestRunner.name} integration test`, () => {
     'Add should be able to add one to a number',
     'Add should be able negate a number',
     'Add should be able to recognize a negative number',
-    'Add should be able to recognize that 0 is not a negative number',
     'Circle should have a circumference of 2PI when the radius is 1',
   ];
 
@@ -126,6 +125,26 @@ describe(`${JestTestRunner.name} integration test`, () => {
 
       assertions.expectSurvived(runResult);
     });
+
+    it('should be able to let a mutant survive after killing mutant 1', async () => {
+      // Arrange
+      const exampleProjectRoot = getProjectRoot('exampleProject');
+      process.chdir(getProjectRoot('exampleProject'));
+      const jestTestRunner = createSut();
+      const mutantRunOptions = factory.mutantRunOptions({
+        sandboxFileName: require.resolve(path.resolve(exampleProjectRoot, 'src', 'Add.js')),
+      });
+      mutantRunOptions.activeMutant.id = 1;
+
+      // Act
+      const firstResult = await jestTestRunner.mutantRun(mutantRunOptions);
+      mutantRunOptions.activeMutant.id = 5;
+      const secondResult = await jestTestRunner.mutantRun(mutantRunOptions);
+
+      // Assert
+      assertions.expectKilled(firstResult);
+      assertions.expectSurvived(secondResult);
+    });
   });
 });
 

packages/jest-runner/test/unit/JestTestRunner.spec.ts

@@ -223,15 +223,10 @@ describe(JestTestRunner.name, () => {
       expect(jestTestAdapterMock.run).calledWithExactly(sinon.match.object, sinon.match.string, undefined);
     });
 
-    it('should set the active mutant in globals', async () => {
+    it('should set the active mutant in environment variables', async () => {
       const sut = createSut();
       await sut.mutantRun(factory.mutantRunOptions({ activeMutant: factory.mutant({ id: 25 }) }));
-      expect(jestTestAdapterMock.run).calledWithMatch(
-        sinon.match({
-          globals: { [INSTRUMENTER_CONSTANTS.ACTIVE_MUTANT]: 25 },
-        }),
-        sinon.match.string
-      );
+      expect(process.env[INSTRUMENTER_CONSTANTS.ACTIVE_MUTANT_ENV_VARIABLE]).to.equal('25');
     });
 
     it('should allow for other globals', async () => {
@@ -245,7 +240,7 @@ describe(JestTestRunner.name, () => {
       await sut.mutantRun(factory.mutantRunOptions({ activeMutant: factory.mutant({ id: 25 }) }));
       expect(jestTestAdapterMock.run).calledWithMatch(
         sinon.match({
-          globals: { foo: 'bar', [INSTRUMENTER_CONSTANTS.ACTIVE_MUTANT]: 25 },
+          globals: { foo: 'bar' },
         }),
         sinon.match.string
       );

packages/jest-runner/testResources/exampleProject/src/Add.js

@@ -1,30 +1,21 @@
 // @ts-nocheck
-var __global_69fa48 = function (g) {
-  g.__mutantCoverage__ = g.__mutantCoverage__ || {
-    static: {},
-    perTest: {}
-  };
-
+var __global_69fa48 = (function(g){
+  if (g.__activeMutant__ === undefined && g.process && g.process.env && g.process.env.__STRYKER_ACTIVE_MUTANT__) {
+    g.__activeMutant__ = Number(g.process.env.__STRYKER_ACTIVE_MUTANT__);
+  }
+  g.__mutantCoverage__ = g.__mutantCoverage__ || { static: {}, perTest: {} };
   g.__coverMutant__ = g.__coverMutant__ || function () {
     var c = g.__mutantCoverage__.static;
-
     if (g.__currentTestId__) {
-      c = g.__mutantCoverage__.perTest[g.__currentTestId__] = g.__mutantCoverage__.perTest[g.__currentTestId__] || {};
+      c = g.__mutantCoverage__.perTest[g.__currentTestId__] =  g.__mutantCoverage__.perTest[g.__currentTestId__] || {};
     }
-
     var a = arguments;
-
-    for (var i = 0; i < a.length; i++) {
+    for(var i=0; i < a.length; i++){
       c[a[i]] = (c[a[i]] || 0) + 1;
     }
   };
-
-  if(g.process && g.process.env && g.process.env.__ACTIVE_MUTANT__) {
-    g.__activeMutant__ = Number(g.process.env.__ACTIVE_MUTANT__);
-  }
-
   return g;
-}(new Function("return this")());
+})(new Function("return this")())
 
 exports.add = function (num1, num2) {
   switch (__global_69fa48.__activeMutant__) {

packages/jest-runner/testResources/exampleProject/src/Circle.js

@@ -1,30 +1,21 @@
 // @ts-nocheck
-var __global_69fa48 = function (g) {
-  g.__mutantCoverage__ = g.__mutantCoverage__ || {
-    static: {},
-    perTest: {}
-  };
-
+var __global_69fa48 = (function(g){
+  if (g.__activeMutant__ === undefined && g.process && g.process.env && g.process.env.__STRYKER_ACTIVE_MUTANT__) {
+    g.__activeMutant__ = Number(g.process.env.__STRYKER_ACTIVE_MUTANT__);
+  }
+  g.__mutantCoverage__ = g.__mutantCoverage__ || { static: {}, perTest: {} };
   g.__coverMutant__ = g.__coverMutant__ || function () {
     var c = g.__mutantCoverage__.static;
-
     if (g.__currentTestId__) {
-      c = g.__mutantCoverage__.perTest[g.__currentTestId__] = g.__mutantCoverage__.perTest[g.__currentTestId__] || {};
+      c = g.__mutantCoverage__.perTest[g.__currentTestId__] =  g.__mutantCoverage__.perTest[g.__currentTestId__] || {};
     }
-
     var a = arguments;
-
-    for (var i = 0; i < a.length; i++) {
+    for(var i=0; i < a.length; i++){
       c[a[i]] = (c[a[i]] || 0) + 1;
     }
   };
-
-  if(g.process && g.process.env && g.process.env.__ACTIVE_MUTANT__) {
-    g.__activeMutant__ = Number(g.process.env.__ACTIVE_MUTANT__);
-  }
-
   return g;
-}(new Function("return this")());
+})(new Function("return this")())
 
 exports.getCircumference = function (radius) {
   switch (__global_69fa48.__activeMutant__) {

packages/jest-runner/testResources/exampleProject/src/__tests__/AddSpec.js

@@ -40,11 +40,4 @@ describe('Add', function() {
     expect(isNegative).toBe(true);
   });
 
-  it('should be able to recognize that 0 is not a negative number', function() {
-    var number = 0;
-
-    var isNegative = isNegativeNumber(number);
-
-    expect(isNegative).toBe(false);
-  });
-});
+});

packages/jest-runner/testResources/exampleProjectWithDefaultJestConfig/src/__tests__/AddSpec.js

@@ -40,11 +40,4 @@ describe('Add', function() {
     expect(isNegative).toBe(true);
   });
 
-  it('should be able to recognize that 0 is not a negative number', function() {
-    var number = 0;
-
-    var isNegative = isNegativeNumber(number);
-
-    expect(isNegative).toBe(false);
-  });
-});
+});

packages/jest-runner/testResources/exampleProjectWithExplicitJestConfig/src/__tests__/AddSpec.js

@@ -40,11 +40,4 @@ describe('Add', function() {
     expect(isNegative).toBe(true);
   });
 
-  it('should be able to recognize that 0 is not a negative number', function() {
-    var number = 0;
-
-    var isNegative = isNegativeNumber(number);
-
-    expect(isNegative).toBe(false);
-  });
-});
+});