fix(config): verify testMatchPatterns contain RegExp instance or string

src/config/__snapshots__/config-set.spec.ts.snap

@@ -18,7 +18,7 @@ Object {
 }
 `;
 
-exports[`jest should returns correct config and go thru backports 1`] = `
+exports[`jest should return correct config and go thru backports 1`] = `
 Object {
   "__backported": true,
   "globals": Object {},
@@ -126,6 +126,32 @@ Array [
 ]
 `;
 
+exports[`testMatchPatterns should return an array of patterns based on testRegex and testMatch from jestConfig 1`] = `
+Array [
+  "**/__tests__/**/*.[jt]s?(x)",
+  "**/?(*.)+(spec|test).[jt]s?(x)",
+]
+`;
+
+exports[`testMatchPatterns should return an array of patterns based on testRegex and testMatch from jestConfig 2`] = `
+Array [
+  /\\.\\*\\\\\\.\\(spec\\|test\\)\\\\\\.\\[jt\\]sx\\?\\$/,
+]
+`;
+
+exports[`testMatchPatterns should return an array of patterns based on testRegex and testMatch from jestConfig 3`] = `
+Array [
+  "**/?(*.)+(spec|test).[tj]s?(x)",
+]
+`;
+
+exports[`testMatchPatterns should return an array of patterns based on testRegex and testMatch from jestConfig 4`] = `
+Array [
+  "**/?(*.)+(spec|test).[tj]s?(x)",
+  "**/?(*.)+(foo|bar).[tj]s?(x)",
+]
+`;
+
 exports[`tsJest should return correct defaults 1`] = `
 Object {
   "babelConfig": undefined,

src/config/config-set.spec.ts

@@ -122,7 +122,7 @@ describe('projectPackageJson', () => {
 })
 
 describe('jest', () => {
-  it('should returns correct config and go thru backports', () => {
+  it('should return correct config and go thru backports', () => {
     expect(createConfigSet().jest).toMatchSnapshot()
     expect(backports.backportJestConfig).toHaveBeenCalledTimes(1)
   })
@@ -150,6 +150,37 @@ describe('jest', () => {
   })
 })
 
+describe('testMatchPatterns', () => {
+  it.each([
+    {
+      jestConfig: {
+        testRegex: [{}],
+        testMatch: [],
+      } as any,
+    },
+    {
+      jestConfig: {
+        testMatch: [],
+        testRegex: [/.*\.(spec|test)\.[jt]sx?$/],
+      } as any,
+    },
+    {
+      jestConfig: {
+        testMatch: ['**/?(*.)+(spec|test).[tj]s?(x)'],
+        testRegex: [],
+      } as any,
+    },
+    {
+      jestConfig: {
+        testMatch: ['**/?(*.)+(spec|test).[tj]s?(x)'],
+        testRegex: ['**/?(*.)+(foo|bar).[tj]s?(x)'],
+      } as any,
+    },
+  ])('should return an array of patterns based on testRegex and testMatch from jestConfig', config => {
+    expect(createConfigSet(config).testMatchPatterns).toMatchSnapshot()
+  })
+})
+
 describe('tsJest', () => {
   const getConfigSet = (tsJest?: TsJestGlobalOptions) => createConfigSet({ tsJestConfig: tsJest })
   const getTsJest = (tsJest?: TsJestGlobalOptions) => getConfigSet(tsJest).tsJest

src/config/config-set.ts

@@ -25,6 +25,7 @@ import {
 
 import { digest as MY_DIGEST, version as MY_VERSION } from '..'
 import { createCompilerInstance } from '../compiler/instance'
+import { DEFAULT_JEST_TEST_MATCH } from '../constants'
 import { internals as internalAstTransformers } from '../transformers'
 import {
   AstTransformerDesc,
@@ -197,7 +198,18 @@ export class ConfigSet {
    */
   @Memoize()
   get testMatchPatterns(): (string | RegExp)[] {
-    return [...this.jest.testMatch, ...this.jest.testRegex]
+    const matchablePatterns = [...this.jest.testMatch, ...this.jest.testRegex].filter(pattern => {
+      /**
+       * jest config testRegex doesn't always deliver the correct RegExp object
+       * See https://github.com/facebook/jest/issues/9778
+       */
+      return pattern instanceof RegExp || typeof pattern === 'string'
+    })
+    if (!matchablePatterns.length) {
+      matchablePatterns.push(...DEFAULT_JEST_TEST_MATCH)
+    }
+
+    return matchablePatterns
   }
 
   /**

src/constants.ts

@@ -1,6 +1,25 @@
+/**
+ * @internal
+ */
 export const LINE_FEED = '\n'
-
+/**
+ * @internal
+ */
 export const EXTENSION_REGEX = /\.[^.]+$/
+/**
+ * @internal
+ */
 export const TS_TSX_REGEX = /\.tsx?$/
+/**
+ * @internal
+ */
 export const JS_JSX_REGEX = /\.jsx?$/
+/**
+ * @internal
+ */
 export const JSON_REGEX = /\.json$/i
+/**
+ * @internal
+ * See https://jestjs.io/docs/en/configuration#testmatch-arraystring
+ */
+export const DEFAULT_JEST_TEST_MATCH = ['**/__tests__/**/*.[jt]s?(x)', '**/?(*.)+(spec|test).[jt]s?(x)']