Is there a way to run some tests sequentially with Jest?

Question

Jest runs your test suite in parallel by default, but there is a flag (--runInBand) that allows you to run the whole suite sequentially (as pointed out here)

Answer 1

This was a bit of a lift, but I think it's worth posting my final config. I had this same problem and I extended Joachim Lous' and Fishball's answers to get to a satisfactory result. Here's my final setup:

An abbreviated directory listing of my project:

├── src
│   ├── index.ts
│   ├── Io.ts
│   ├── Modules
│   │   └── index.ts
│   └── .....
└── tests
    ├── EndToEnd
    │   ├── Fixtures.ts
    │   ├── Mq.spec.ts
    │   ├── LegalEntities.spec.ts
    │   └── Utils.ts
    └── UnitTests
        ├── LegalEntities.spec.ts
        ├── Assets.spec.ts
        └── Utils.ts

My (abbreviated) package.json file with my jest configs in it:

{
  "name": "my-project",
  "scripts": {
    "build": "scripts/build",
    "check": "tsc --noEmit",
    "test": "jest"
  },
  "....": "....",
  "jest": {
    "projects": [
      {
        "displayName": "unit-tests",
        "testEnvironment": "node",
        "verbose": true,
        "testMatch": [
          "/tests/**/*.spec.ts",
          "!**/EndToEnd/**/*.spec.ts"
        ],
        "transform": {
          "^.+\\.tsx?$": "ts-jest"
        }
      },
      {
        "displayName": "e2e-tests",
        "testEnvironment": "node",
        "verbose": true,
        "maxWorkers": 1,
        "testMatch": [
          "/tests/EndToEnd/**/*.spec.ts"   
        ],
        "transform": {
          "^.+\\.tsx?$": "ts-jest"
        }
      }
    ]
  }
}

Things to note:

• When using the projects key in jest, I had to move all config into the individual project blocks. Using project config was mutually-exclusive with using global config.
• I did not use the runner directive as mentioned in other answers. Instead I used the maxWorkers option to limit execution to 1 worker (i.e., inherently serial). This meant I didn't have to use more dependencies.
• For some reason the negation syntax was finicky with my unit tests. I wanted to specify unit tests as all tests that were NOT in the EndToEnd directory, and it took me a few tried to get jest to do this correctly.

Thanks to everyone else for the viable starting point. Hope this helps others!