Validate generated json schemas in the tests

declarations/ajv.js

@@ -0,0 +1,9 @@
+declare module 'ajv' {
+    declare export default class Ajv {
+        errors: {message: string}[];
+
+        constructor(): void;
+
+        validateSchema(schema: mixed): boolean;
+    }
+}

package.json

@@ -37,6 +37,7 @@
         "@babel/preset-env": "^7.0.0-beta.32",
         "@babel/preset-flow": "^7.0.0-beta.32",
         "@babel/register": "^7.0.0-beta.32",
+        "ajv": "^5.5.1",
         "flow-bin": "^0.60.1",
         "jasmine": "^2.8.0",
         "mocha": "^4.0.1",

tests/run.js

@@ -3,6 +3,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import * as yaml from 'yaml-js';
 import wu from 'wu';
+import Ajv from 'ajv';
 
 import collect from '../src';
 
@@ -22,6 +23,14 @@ function run(title) {
     it('should provide expected types', () => {
         assert.deepEqual(actual.types, expected);
     });
+
+    it('should generate valid JSON schema', () => {
+        const ajv = new Ajv;
+
+        ajv.validateSchema(actual.schema);
+
+        assert.equal(ajv.errors, null);
+    });
 }
 
 function detectCycles(obj: mixed, cycles: Set<mixed> = new Set, objs: Set<mixed> = new Set) {