diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 31923b5..15620d1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,3 +23,4 @@ jobs:
           cache: pnpm
       - run: pnpm install
       - run: pnpm run lint
+      - run: pnpm run test
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index afd6005..4acf8d9 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -50,7 +50,7 @@ For major changes requiring RFC:
 
 ## Contributing Test Fixtures
 
-Test fixtures validate TOON implementations across languages. Add your test to `tests/fixtures/encode/` or `tests/fixtures/decode/`, validate against `tests/fixtures.schema.json`, and submit a PR.
+Test fixtures validate TOON implementations across languages. Add your test to `tests/fixtures/encode/` or `tests/fixtures/decode/`, run `pnpm test` to validate it against `tests/fixtures.schema.json`, and submit a PR.
 
 See [tests/README.md](./tests/README.md) for fixture structure and guidelines.
 
diff --git a/package.json b/package.json
index 7641466..9223570 100644
--- a/package.json
+++ b/package.json
@@ -32,10 +32,12 @@
   ],
   "scripts": {
     "lint": "eslint .",
+    "test": "node scripts/validate-fixtures.ts",
     "release": "bumpp"
   },
   "devDependencies": {
     "@antfu/eslint-config": "^9.5.1",
+    "ajv": "^8.20.0",
     "bumpp": "^12.3.0",
     "eslint": "^10.11.0"
   }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 55be21f..e53a3f3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -11,6 +11,9 @@ importers:
       '@antfu/eslint-config':
         specifier: ^9.5.1
         version: 9.5.1(@typescript-eslint/typescript-estree@8.71.0(typescript@6.0.3))(@typescript-eslint/utils@8.71.0(eslint@10.11.0(jiti@2.7.0))(typescript@6.0.3))(@vue/compiler-sfc@3.5.43)(eslint@10.11.0(jiti@2.7.0))(typescript@6.0.3)
+      ajv:
+        specifier: ^8.20.0
+        version: 8.20.0
       bumpp:
         specifier: ^12.3.0
         version: 12.3.0
@@ -390,6 +393,9 @@ packages:
   ajv@6.15.0:
     resolution: {integrity: sha512-fgFx7Hfoq60ytK2c7DhnF8jIvzYgOMxfugjLOSMHjLIPgenqa7S7oaagATUq99mV6IYvN2tRmC0wnTYX6iPbMw==}
 
+  ajv@8.20.0:
+    resolution: {integrity: sha512-Thbli+OlOj+iMPYFBVBfJ3OmCAnaSyNn4M1vz9T6Gka5Jt9ba/HIR56joy65tY6kx/FCF5VXNB819Y7/GUrBGA==}
+
   ansis@4.4.0:
     resolution: {integrity: sha512-9k3v7xcHwgdO/DruxGIg4HtjvlAZlcnsX/mzqUb1t3NkYnl9kK2UJ+Gq0io+vQf7iT//BD/HB/NBkUR1LWxoeA==}
     engines: {node: '>=14'}
@@ -782,6 +788,9 @@ packages:
   fast-string-width@3.0.2:
     resolution: {integrity: sha512-gX8LrtNEI5hq8DVUfRQMbr5lpaS4nMIWV+7XEbXk2b8kiQIizgnlr12B4dA3ZEx3308ze0O4Q1R+cHts8kyUJg==}
 
+  fast-uri@3.1.8:
+    resolution: {integrity: sha512-GZMtZUTNRpOVIECoXwLNZS5xUGE+mVNbTB8h/7Rwh2TFWcBQiPzTgyZi05BF9UMZKkLJv8XBRJTlU7zg8+ZfMg==}
+
   fast-wrap-ansi@0.2.2:
     resolution: {integrity: sha512-7F2Fl+TjRSenLqlU3UjSH0iyqopqoZIu7eZVpEirP2g1GtWa2G/ecEmBdgz31+Mxr+ELclgg6sokpSFIQiZ02Q==}
 
@@ -922,6 +931,9 @@ packages:
   json-schema-traverse@0.4.1:
     resolution: {integrity: sha512-xbbCH5dCYU5T8LcEhhuh7HJ88HXuW3qsI3Y0zOZFKfZEHcpWiHU/Jxzk629Brsab/mMiHQti9wMP+845RPe3Vg==}
 
+  json-schema-traverse@1.0.0:
+    resolution: {integrity: sha512-NM8/P9n3XjXhIZn1lLhkFaACTOURQXjWhV4BA/RnOv8xvgqtqpAX9IO4mRQxSx1Rlo4tqzeqb0sOlruaOy3dug==}
+
   json-stable-stringify-without-jsonify@1.0.1:
     resolution: {integrity: sha512-Bdboy+l7tA3OGW6FjyFHWkP5LuByj1Tk33Ljyq0axyzdk9//JSi2u3fP1QSmd1KNwq6VOKYGlAu87CisVir6Pw==}
 
@@ -1240,6 +1252,10 @@ packages:
     resolution: {integrity: sha512-ycwFAS14Jw4mppvmK4GR/J6u3WpWpjkEApehuHtLc/8VpPNpDMbQ4WjqwplXifGeyKOzHSFLmSPqzksDQE2Sfg==}
     hasBin: true
 
+  require-from-string@2.0.2:
+    resolution: {integrity: sha512-Xf0nWe6RseziFMu+Ap9biiUbmplq6S9/p+7w7YXP/JBHhrUDDUhwa+vANyubuqfZWTveU//DYVGsDG7RKL/vEw==}
+    engines: {node: '>=0.10.0'}
+
   reserved-identifiers@1.2.0:
     resolution: {integrity: sha512-yE7KUfFvaBFzGPs5H3Ops1RevfUEsDc5Iz65rOwWg4lE8HJSYtle77uul3+573457oHvBKuHYDl/xqUkKpEEdw==}
     engines: {node: '>=18'}
@@ -1828,6 +1844,13 @@ snapshots:
       json-schema-traverse: 0.4.1
       uri-js: 4.4.1
 
+  ajv@8.20.0:
+    dependencies:
+      fast-deep-equal: 3.1.3
+      fast-uri: 3.1.8
+      json-schema-traverse: 1.0.0
+      require-from-string: 2.0.2
+
   ansis@4.4.0: {}
 
   are-docs-informative@0.1.1: {}
@@ -2252,6 +2275,8 @@ snapshots:
     dependencies:
       fast-string-truncated-width: 3.0.3
 
+  fast-uri@3.1.8: {}
+
   fast-wrap-ansi@0.2.2:
     dependencies:
       fast-string-width: 3.0.2
@@ -2363,6 +2388,8 @@ snapshots:
 
   json-schema-traverse@0.4.1: {}
 
+  json-schema-traverse@1.0.0: {}
+
   json-stable-stringify-without-jsonify@1.0.1: {}
 
   jsonc-eslint-parser@3.3.0:
@@ -2881,6 +2908,8 @@ snapshots:
     dependencies:
       jsesc: 3.1.0
 
+  require-from-string@2.0.2: {}
+
   reserved-identifiers@1.2.0: {}
 
   resolve-pkg-maps@1.0.0: {}
diff --git a/scripts/validate-fixtures.ts b/scripts/validate-fixtures.ts
new file mode 100644
index 0000000..045f11d
--- /dev/null
+++ b/scripts/validate-fixtures.ts
@@ -0,0 +1,29 @@
+import { readdir, readFile } from 'node:fs/promises'
+import { join } from 'node:path'
+import process from 'node:process'
+import Ajv from 'ajv'
+
+const testsDir = join(import.meta.dirname, '../tests')
+const schema = JSON.parse(await readFile(join(testsDir, 'fixtures.schema.json'), 'utf8'))
+const validate = new Ajv({ allErrors: true }).compile(schema)
+
+const fixtureErrors: string[] = []
+for (const category of ['encode', 'decode']) {
+  const categoryDir = join(testsDir, 'fixtures', category)
+  const fileNames = (await readdir(categoryDir)).filter(fileName => fileName.endsWith('.json'))
+  for (const fileName of fileNames) {
+    const fixture = JSON.parse(await readFile(join(categoryDir, fileName), 'utf8'))
+    const fixturePath = `${category}/${fileName}`
+    if (!validate(fixture))
+      fixtureErrors.push(...validate.errors!.map(error => `${fixturePath}: ${error.instancePath || '/'} ${error.message}`))
+    if (fixture.category !== category)
+      fixtureErrors.push(`${fixturePath}: /category is "${fixture.category}", expected "${category}"`)
+  }
+}
+
+if (fixtureErrors.length > 0) {
+  console.error(fixtureErrors.join('\n'))
+  process.exit(1)
+}
+
+console.log('All fixtures match tests/fixtures.schema.json')
diff --git a/tests/README.md b/tests/README.md
index b06f6e0..6993848 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -148,17 +148,8 @@ Load each fixture file, run every entry in its `tests` array through your encode
 
 ## Validating Fixtures
 
-All fixture files should validate against [`fixtures.schema.json`](./fixtures.schema.json). Run the commands below from the repository root:
-
-```bash
-# Using ajv-cli
-npx ajv-cli validate -s tests/fixtures.schema.json -d "tests/fixtures/**/*.json"
-
-# Using check-jsonschema (Python)
-pip install check-jsonschema
-check-jsonschema --schemafile tests/fixtures.schema.json tests/fixtures/**/*.json
-```
+`pnpm test` validates every fixture against [`fixtures.schema.json`](./fixtures.schema.json) and checks that its `category` matches its directory.
 
 ## Contributing Test Cases
 
-Add your test to the matching fixture file, reference the spec section it exercises, verify the expected output against SPEC.md, and validate the file against the schema before submitting a PR. See [CONTRIBUTING.md](../CONTRIBUTING.md) for guidelines.
+Add your test to the matching fixture file, reference the spec section it exercises, verify the expected output against SPEC.md, and run `pnpm test` before submitting a PR. See [CONTRIBUTING.md](../CONTRIBUTING.md) for guidelines.