3 files changed, 100 insertions, 0 deletions
diff --git a/spec/frontend/__helpers__/matchers/index.js b/spec/frontend/__helpers__/matchers/index.js
index 76571bafb06..9b83ced10e1 100644
--- a/spec/frontend/__helpers__/matchers/index.js
+++ b/spec/frontend/__helpers__/matchers/index.js
@@ -1,3 +1,4 @@
 export * from './to_have_sprite_icon';
 export * from './to_have_tracking_attributes';
 export * from './to_match_interpolated_text';
+export * from './to_validate_json_schema';
diff --git a/spec/frontend/__helpers__/matchers/to_validate_json_schema.js b/spec/frontend/__helpers__/matchers/to_validate_json_schema.js
new file mode 100644
index 00000000000..ff391f08c55
--- /dev/null
+++ b/spec/frontend/__helpers__/matchers/to_validate_json_schema.js
@@ -0,0 +1,34 @@
+// NOTE: Make sure to initialize ajv when using this helper
+
+const getAjvErrorMessage = ({ errors }) => {
+  return (errors || []).map((error) => {
+    return `Error with item ${error.instancePath}: ${error.message}`;
+  });
+};
+
+export function toValidateJsonSchema(testData, validator) {
+  if (!(validator instanceof Function && validator.schema)) {
+    return {
+      validator,
+      message: () =>
+        'Validator must be a validating function with property "schema", created with `ajv.compile`. See https://ajv.js.org/api.html#ajv-compile-schema-object-data-any-boolean-promise-any.',
+      pass: false,
+    };
+  }
+
+  const isValid = validator(testData);
+
+  return {
+    actual: testData,
+    message: () => {
+      if (isValid) {
+        // We can match, but still fail because we're in a `expect...not.` context
+        return 'Expected the given data not to pass the schema validation, but found that it was considered valid.';
+      }
+
+      const errorMessages = getAjvErrorMessage(validator).join('\n');
+      return `Expected the given data to pass the schema validation, but found that it was considered invalid. Errors:\n${errorMessages}`;
+    },
+    pass: isValid,
+  };
+}
diff --git a/spec/frontend/__helpers__/matchers/to_validate_json_schema_spec.js b/spec/frontend/__helpers__/matchers/to_validate_json_schema_spec.js
new file mode 100644
index 00000000000..fd42c710c65
--- /dev/null
+++ b/spec/frontend/__helpers__/matchers/to_validate_json_schema_spec.js
@@ -0,0 +1,65 @@
+import Ajv from 'ajv';
+import AjvFormats from 'ajv-formats';
+
+const JSON_SCHEMA = {
+  type: 'object',
+  properties: {
+    fruit: {
+      type: 'string',
+      minLength: 3,
+    },
+  },
+};
+
+const ajv = new Ajv({
+  strictTypes: false,
+  strictTuples: false,
+  allowMatchingProperties: true,
+});
+
+AjvFormats(ajv);
+const schema = ajv.compile(JSON_SCHEMA);
+
+describe('custom matcher toValidateJsonSchema', () => {
+  it('throws error if validator is not compiled correctly', () => {
+    expect(() => {
+      expect({}).toValidateJsonSchema({});
+    }).toThrow(
+      'Validator must be a validating function with property "schema", created with `ajv.compile`. See https://ajv.js.org/api.html#ajv-compile-schema-object-data-any-boolean-promise-any.',
+    );
+  });
+
+  describe('positive assertions', () => {
+    it.each`
+      description      | input
+      ${'valid input'} | ${{ fruit: 'apple' }}
+    `('schema validation passes for $description', ({ input }) => {
+      expect(input).toValidateJsonSchema(schema);
+    });
+
+    it('throws if not matching', () => {
+      expect(() => expect(null).toValidateJsonSchema(schema)).toThrowError(
+        `Expected the given data to pass the schema validation, but found that it was considered invalid. Errors:
+Error with item : must be object`,
+      );
+    });
+  });
+
+  describe('negative assertions', () => {
+    it.each`
+      description                    | input
+      ${'no input'}                  | ${null}
+      ${'input with invalid type'}   | ${'banana'}
+      ${'input with invalid length'} | ${{ fruit: 'aa' }}
+      ${'input with invalid type'}   | ${{ fruit: 12345 }}
+    `('schema validation fails for $description', ({ input }) => {
+      expect(input).not.toValidateJsonSchema(schema);
+    });
+
+    it('throws if matching', () => {
+      expect(() => expect({ fruit: 'apple' }).not.toValidateJsonSchema(schema)).toThrowError(
+        'Expected the given data not to pass the schema validation, but found that it was considered valid.',
+      );
+    });
+  });
+});