【Jest】「`outDir` in your tsconfig is neither ` ... ''～...」

解決策

• tsconfig.jsonのnoEmitOrErrorをfalseにする
• 参考1：https://github.com/kulshekhar/ts-jest/issues/4246
• 参考2：https://github.com/kulshekhar/ts-jest/issues/4207

背景

jestを実行したら以下のエラーが出力された

> src@1.0.0 test
> jest ./tests/sample.test.ts

 FAIL  tests/sample.test.ts
  ● Test suite failed to run

    Unable to process '/home/dev1/src/backEnd/tests/sample.test.ts', please make sure that `outDir` in your tsconfig is neither `''` or `'.'`. You can also configure Jest config option `transformIgnorePatterns` to inform `ts-jest` to transform /home/dev1/src/backEnd/tests/sample.test.ts

      at TsCompiler.getCompiledOutput (node_modules/ts-jest/dist/legacy/compiler/ts-compiler.js:170:27)
      at TsJestCompiler.getCompiledOutput (node_modules/ts-jest/dist/legacy/compiler/ts-jest-compiler.js:14:39)
      at TsJestTransformer.processWithTs (node_modules/ts-jest/dist/legacy/ts-jest-transformer.js:255:37)
      at TsJestTransformer.process (node_modules/ts-jest/dist/legacy/ts-jest-transformer.js:184:24)
      at ScriptTransformer.transformSource (node_modules/@jest/transform/build/ScriptTransformer.js:545:31)
      at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:674:40)
      at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:726:19)
~ 省略 ~

エラーメッセージは

1. プロセスが使えない

Unable to process '/home/dev1/src/backEnd/tests/sample.test.ts',

2. tsconfig.jsonのoutDirに問題あり

please make sure that outDir in your tsconfig is neither '' or '.'.

3. transformIgnorePatternsを設定して

You can also configure Jest config option transformIgnorePatterns to inform ts-jest to transform /home/dev1/src/backEnd/tests/sample.test.ts

の3点

しかし、tsconfig.jsonのoutdirは./dist、transformIgnorePatternsにはnode_modulesをそれぞれ記載済みだった。そのため、メッセージ以外の箇所にエラー原因があると推察し調査を実施した

調査結果

https://github.com/kulshekhar/ts-jest/issues/2407
様々なサイトを確認し、このissueの通りtsconfig.jsonのnoEmitOrErrorをfalseにしたらjestが実行できた

> src@1.0.0 test
> jest ./tests/sample.test.ts

 PASS  tests/sample.test.ts (7.583 s)
  ✓ test (5 ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |       0 |        0 |       0 |       0 |                   
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        8.747 s
Ran all test suites matching /.\/tests\/sample.test.ts/i.

sample.test.ts

//動けばいい
it('test', () => {
  expect(1).toBe(1);
});

最後に

備忘録として残すのが優先のため、原因調査は気が向いたら行う