With typescript some of these mutations make no sense, or do they? Should I just ignore them?

[kswope]

Here's a few mutations in very simple functions I'm having trouble with

(some output of stryker run)

[NoCoverage] BlockStatement
backend/src/test/dummies.ts:44:25
-   export function title() {
-     return chance.sentence()
-   }
+   export function title() {}

^ How would wiping out the entire function body ever be something I should account for in a test?

[Survived] ObjectLiteral
backend/src/test/dummies.ts:19:22
-     return chance.word({ length: 15 })
+     return chance.word({})

^ Passing hard coded parameters to a library function also doesn't seem like something that would be relevant to a test.

[Survived] StringLiteral
backend/src/dal/locations.ts:5:53
-   export async function create(userId: number, name = "default"): Promise<number> {
+   export async function create(userId: number, name = ""): Promise<number> {

^ This would make sense where string is used in a boolean context, but why would mutating a default argument make any sense?

[nicojs]

These mutations don't make sense indeed. If you want to filter them out, you should enable the TypeScript checker plugin

F.y.i. using the TypeScript checker is a tradeoff. On the one hand, mutants will be more accurate, on the other hand, it will take more time.

[kswope]

These mutations don't make sense indeed. If you want to filter them out, you should enable the TypeScript checker plugin

F.y.i. using the TypeScript checker is a tradeoff. On the one hand, mutants will be more accurate, on the other hand, it will take more time.

I got all those errors while using the typescript-checker.

[nicojs]

Could you share your config and logging after running with --fileLogLevel trace?

[kswope]

// @ts-check
/** @type {import('@stryker-mutator/api/core').PartialStrykerOptions} */
const config = {
  _comment: "This config was generated using 'stryker init'.",
  testRunner: "vitest",
  mutate: ["*/**/!(*.test).ts"],
  // mutate: ["!backend/src/**/*.test.ts", "backend/src/**/dummies.ts"],
  reporters: ["progress", "clear-text", "html"],
  // mutator: {
  //   excludedMutations: ["ObjectLiteral", "BlockStatement", "StringLiteral"],
  // },
}
export default config

stryker.log

[nicojs]

I can see you've installed the TypeScript checker, but you didn't configure it. Could try again?

// @ts-check
/** @type {import('@stryker-mutator/api/core').PartialStrykerOptions} */
const config = {
  _comment: "This config was generated using 'stryker init'.",
  testRunner: "vitest",
  mutate: ["*/**/!(*.test).ts"],
+ checkers: ["typescript"],
  // mutate: ["!backend/src/**/*.test.ts", "backend/src/**/dummies.ts"],
  reporters: ["progress", "clear-text", "html"],
  // mutator: {
  //   excludedMutations: ["ObjectLiteral", "BlockStatement", "StringLiteral"],
  // },
}
export default config

[kswope]

Somehow I got the impression from the docs that you only needed to load the plugin and not configure if you wanted something other than the default. So I copied the example config.

const config = {
  _comment: "This config was generated using 'stryker init'.",
  checkers: ["typescript"],
  tsconfigFile: "tsconfig.json",
  typescriptChecker: {
    prioritizePerformanceOverAccuracy: true,
  },
  testRunner: "vitest",
  mutate: ["*/**/!(*.test).ts"],
  // mutate: ["!backend/src/**/*.test.ts", "backend/src/**/dummies.ts"],
  reporters: ["progress", "clear-text", "html"],
  // mutator: {
  //   excludedMutations: ["ObjectLiteral", "BlockStatement", "StringLiteral"],
  // },
}
export default config

Nothing changed. I'm not sure what we are expecting since the code for that typescript plugin doesn't mention any of those mutations anyway.