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feat: improve expectTypeOf error messages (#4206)
Co-authored-by: Misha Kaletsky <[email protected]> Co-authored-by: Vladimir Sheremet <[email protected]>
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Misha Kaletsky
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GitHub
co-authored by
Misha Kaletsky
Vladimir Sheremet
Misha Kaletsky
Vladimir Sheremet
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255d95d4ae
commit
33a5402e69
@@ -42,6 +42,7 @@ Next generation testing framework powered by Vite.
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- Workers multi-threading via [Tinypool](https://github.com/tinylibs/tinypool) (a lightweight fork of [Piscina](https://github.com/piscinajs/piscina))
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- Benchmarking support with [Tinybench](https://github.com/tinylibs/tinybench)
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- [Workspace](https://vitest.dev/guide/workspace) support
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- [expect-type](https://github.com/mmkal/expect-type) for type-level testing
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- ESM first, top level await
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- Out-of-box TypeScript / JSX support
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- Filtering, timeouts, concurrent for suite and tests
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@@ -31,17 +31,62 @@ You can see a list of possible matchers in [API section](/api/expect-typeof).
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## Reading Errors
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If you are using `expectTypeOf` API, you might notice hard to read errors or unexpected:
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If you are using `expectTypeOf` API, refer to the [expect-type documentation on its error messages](https://github.com/mmkal/expect-type#error-messages).
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When types don't match, `.toEqualTypeOf` and `.toMatchTypeOf` use a special helper type to produce error messages that are as actionable as possible. But there's a bit of an nuance to understanding them. Since the assertions are written "fluently", the failure should be on the "expected" type, not the "actual" type (`expect<Actual>().toEqualTypeOf<Expected>()`). This means that type errors can be a little confusing - so this library produces a `MismatchInfo` type to try to make explicit what the expectation is. For example:
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```ts
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expectTypeOf(1).toEqualTypeOf<string>()
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// ^^^^^^^^^^^^^^^^^^^^^^
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// index-c3943160.d.ts(90, 20): Arguments for the rest parameter 'MISMATCH' were not provided.
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expectTypeOf({ a: 1 }).toEqualTypeOf<{ a: string }>()
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```
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This is due to how [`expect-type`](https://github.com/mmkal/expect-type) handles type errors.
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Is an assertion that will fail, since `{a: 1}` has type `{a: number}` and not `{a: string}`. The error message in this case will read something like this:
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Unfortunately, TypeScript doesn't provide type metadata without patching, so we cannot provide useful error messages at this point, but there are <a href="https://github.com/microsoft/TypeScript/pull/40468" target="_blank">works in TypeScript project</a> to fix this. If you want better messages, please, ask TypeScript team to have a look at mentioned PR.
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```
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test/test.ts:999:999 - error TS2344: Type '{ a: string; }' does not satisfy the constraint '{ a: \\"Expected: string, Actual: number\\"; }'.
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Types of property 'a' are incompatible.
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Type 'string' is not assignable to type '\\"Expected: string, Actual: number\\"'.
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999 expectTypeOf({a: 1}).toEqualTypeOf<{a: string}>()
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```
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Note that the type constraint reported is a human-readable messaging specifying both the "expected" and "actual" types. Rather than taking the sentence `Types of property 'a' are incompatible // Type 'string' is not assignable to type "Expected: string, Actual: number"` literally - just look at the property name (`'a'`) and the message: `Expected: string, Actual: number`. This will tell you what's wrong, in most cases. Extremely complex types will of course be more effort to debug, and may require some experimentation. Please [raise an issue](https://github.com/mmkal/expect-type) if the error messages are actually misleading.
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The `toBe...` methods (like `toBeString`, `toBeNumber`, `toBeVoid` etc.) fail by resolving to a non-callable type when the `Actual` type under test doesn't match up. For example, the failure for an assertion like `expectTypeOf(1).toBeString()` will look something like this:
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```
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test/test.ts:999:999 - error TS2349: This expression is not callable.
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Type 'ExpectString<number>' has no call signatures.
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999 expectTypeOf(1).toBeString()
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~~~~~~~~~~
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```
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The `This expression is not callable` part isn't all that helpful - the meaningful error is the next line, `Type 'ExpectString<number> has no call signatures`. This essentially means you passed a number but asserted it should be a string.
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If TypeScript added support for ["throw" types](https://github.com/microsoft/TypeScript/pull/40468) these error messagess could be improved significantly. Until then they will take a certain amount of squinting.
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#### Concrete "expected" objects vs typeargs
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Error messages for an assertion like this:
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```ts
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expectTypeOf({ a: 1 }).toEqualTypeOf({ a: '' })
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```
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Will be less helpful than for an assertion like this:
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```ts
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expectTypeOf({ a: 1 }).toEqualTypeOf<{ a: string }>()
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```
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This is because the TypeScript compiler needs to infer the typearg for the `.toEqualTypeOf({a: ''})` style, and this library can only mark it as a failure by comparing it against a generic `Mismatch` type. So, where possible, use a typearg rather than a concrete type for `.toEqualTypeOf` and `toMatchTypeOf`. If it's much more convenient to compare two concrete types, you can use `typeof`:
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```ts
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const one = valueFromFunctionOne({ some: { complex: inputs } })
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const two = valueFromFunctionTwo({ some: { other: inputs } })
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expectTypeOf(one).toEqualTypeof<typeof two>()
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```
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If you find it hard working with `expectTypeOf` API and figuring out errors, you can always use more simple `assertType` API:
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@@ -171,7 +171,7 @@
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"birpc": "0.2.14",
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"chai-subset": "^1.6.0",
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"cli-truncate": "^4.0.0",
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"expect-type": "^0.16.0",
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"expect-type": "^0.17.3",
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"fast-glob": "^3.3.2",
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"find-up": "^6.3.0",
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"flatted": "^3.2.9",
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@@ -187,7 +187,9 @@ export class Typechecker {
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const suiteErrors = errors.map((info) => {
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const limit = Error.stackTraceLimit
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Error.stackTraceLimit = 0
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const error = new TypeCheckError(info.errMsg, [
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// Some expect-type errors have the most useful information on the second line e.g. `This expression is not callable.\n Type 'ExpectString<number>' has no call signatures.`
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const errMsg = info.errMsg.replace(/\r?\n\s*(Type .* has no call signatures)/g, ' $1')
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const error = new TypeCheckError(errMsg, [
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{
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file: filepath,
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line: info.line,
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@@ -201,7 +203,7 @@ export class Typechecker {
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error: {
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name: error.name,
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nameStr: String(error.name),
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message: info.errMsg,
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message: errMsg,
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stacks: error.stacks,
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stack: '',
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stackStr: '',
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Generated
+4
-4
@@ -1352,8 +1352,8 @@ importers:
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specifier: ^4.0.0
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version: 4.0.0
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expect-type:
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specifier: ^0.16.0
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version: 0.16.0
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specifier: ^0.17.3
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version: 0.17.3
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fast-glob:
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specifier: ^3.3.2
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version: 3.3.2
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@@ -15954,8 +15954,8 @@ packages:
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engines: {node: '>=6'}
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dev: true
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/[email protected]6.0:
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resolution: {integrity: sha512-wCpFeVBiAPGiYkQZzaqvGuuBnNCHbtnowMOBpBGY8a27XbG8VAit3lklWph1r8VmgsH61mOZqI3NuGm8bZnUlw==}
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/[email protected]7.3:
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resolution: {integrity: sha512-K0ZdZJ97jiAtaOwhEHHz/f0N6Xbj5reRz5g6+5BO7+OvqQ7PMQz0/c8bFSJs1zPotNJL5HJaC6t6lGPEAtGyOw==}
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engines: {node: '>=12.0.0'}
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dev: true
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@@ -1,18 +1,18 @@
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// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
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exports[`should fail > typecheck files 1`] = `
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"TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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"TypeCheckError: Type 'string' does not satisfy the constraint '"Expected string, Actual number"'.
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TypeCheckError: This expression is not callable. Type 'ExpectArray<number>' has no call signatures.
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TypeCheckError: This expression is not callable. Type 'ExpectUndefined<number>' has no call signatures.
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures.
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TypeCheckError: Type 'string' does not satisfy the constraint '"Expected string, Actual number"'.
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TypeCheckError: Unused '@ts-expect-error' directive.
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TypeCheckError: Expected 1 arguments, but got 0."
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures."
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`;
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exports[`should fail > typecheck files 2`] = `
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" FAIL fail.test-d.ts > nested suite
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures.
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❯ fail.test-d.ts:15:19
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13| })
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14|
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@@ -34,18 +34,18 @@ TypeCheckError: Unused '@ts-expect-error' directive.
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exports[`should fail > typecheck files 4`] = `
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" FAIL fail.test-d.ts > failing test
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TypeCheckError: Expected 1 arguments, but got 0.
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❯ fail.test-d.ts:4:19
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TypeCheckError: Type 'string' does not satisfy the constraint '"Expected string, Actual number"'.
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❯ fail.test-d.ts:4:33
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2|
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3| test('failing test', () => {
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4| expectTypeOf(1).toEqualTypeOf<string>()
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| ^
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| ^
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5| })"
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`;
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exports[`should fail > typecheck files 5`] = `
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" FAIL fail.test-d.ts > nested suite > nested 2 > failing test 2
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures.
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❯ fail.test-d.ts:10:23
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8| describe('nested 2', () => {
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9| test('failing test 2', () => {
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@@ -56,7 +56,7 @@ TypeCheckError: Expected 1 arguments, but got 0.
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exports[`should fail > typecheck files 6`] = `
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" FAIL fail.test-d.ts > nested suite > nested 2 > failing test 2
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: This expression is not callable. Type 'ExpectUndefined<number>' has no call signatures.
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❯ fail.test-d.ts:11:23
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9| test('failing test 2', () => {
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10| expectTypeOf(1).toBeVoid()
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@@ -67,7 +67,7 @@ TypeCheckError: Expected 1 arguments, but got 0.
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exports[`should fail > typecheck files 7`] = `
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" FAIL js-fail.test-d.js > js test fails
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: This expression is not callable. Type 'ExpectArray<number>' has no call signatures.
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❯ js-fail.test-d.js:6:19
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4|
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5| test('js test fails', () => {
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@@ -78,12 +78,12 @@ TypeCheckError: Expected 1 arguments, but got 0.
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exports[`should fail > typecheck files 8`] = `
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" FAIL only.test-d.ts > failing test
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TypeCheckError: Expected 1 arguments, but got 0.
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❯ only.test-d.ts:4:19
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TypeCheckError: Type 'string' does not satisfy the constraint '"Expected string, Actual number"'.
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❯ only.test-d.ts:4:33
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2|
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3| test.only('failing test', () => {
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4| expectTypeOf(1).toEqualTypeOf<string>()
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| ^
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| ^
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5| })"
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`;
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@@ -99,8 +99,8 @@ Error: error TS18003: No inputs were found in config file '<root>/tsconfig.vites
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`;
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exports[`should fail > typecheks with custom tsconfig 1`] = `
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"TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0.
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TypeCheckError: Expected 1 arguments, but got 0."
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"TypeCheckError: This expression is not callable. Type 'ExpectUndefined<number>' has no call signatures.
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures.
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TypeCheckError: Type 'string' does not satisfy the constraint '"Expected string, Actual number"'.
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TypeCheckError: This expression is not callable. Type 'ExpectVoid<number>' has no call signatures."
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`;
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