test: introduces custom chai assertions

.eslintrc.js

@@ -12,6 +12,10 @@ module.exports = {
     'no-plusplus': 'off',
     'func-names': 'off',
 
+    // Disabled to allow "expect()" assertions with parameters:
+    // expect(foo).to.be.valid
+    'no-unused-expressions': 'off',
+
     // Temporary overrides. Logic to be rewritten.
     // TODO https://github.com/apiaryio/gavel.js/issues/150
     'no-param-reassign': 'off'

test/chai.js

@@ -0,0 +1,203 @@
+/* eslint-disable no-underscore-dangle */
+const chai = require('chai');
+
+const stringify = (obj) => {
+  return JSON.stringify(obj, null, 2);
+};
+
+chai.use(({ Assertion }, utils) => {
+  const createErrorPropertyAssertion = (propName, methodName) => {
+    Assertion.addMethod(methodName, function(expectedValue) {
+      const stringifiedObj = stringify(this._obj);
+      const { currentError: error, currentErrorIndex } = this.__flags;
+      const target = error[propName];
+      const isRegExp = expectedValue instanceof RegExp;
+      const matchWord = isRegExp ? 'matches' : 'equals';
+
+      new Assertion(error).to.be.instanceOf(Object);
+      new Assertion(error).to.have.property(propName);
+
+      this.assert(
+        isRegExp ? expectedValue.test(target) : target === expectedValue,
+        `
+  Expected the next HTTP message field:
+
+  ${stringifiedObj}
+
+  to have ${propName} at index ${currentErrorIndex} that ${matchWord}:
+
+  ${expectedValue.toString()}
+
+  but got:
+
+  ${target.toString()}
+  `,
+        `
+  Expected the next HTTP message field:
+
+  ${stringifiedObj}
+
+  not to have ${propName} at index ${currentErrorIndex}, but got:
+
+  ${target.toString()}
+  `,
+        expectedValue.toString(),
+        target.toString(),
+        true
+      );
+    });
+  };
+
+  createErrorPropertyAssertion('message', 'withMessage');
+  createErrorPropertyAssertion('pointer', 'withPointer');
+
+  utils.addProperty(Assertion.prototype, 'valid', function() {
+    const { isValid } = this._obj;
+    const stringifiedObj = stringify(this._obj);
+
+    this.assert(
+      isValid === true,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have "isValid" equal #{exp}, but got #{act}'.
+`,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to be invalid, but it is actually valid.`,
+      { isValid },
+      { isValid: true },
+      true
+    );
+  });
+
+  utils.addProperty(Assertion.prototype, 'errors', function() {
+    const { errors } = this._obj;
+    const stringifiedObj = stringify(this._obj);
+
+    this.assert(
+      errors.length > 0,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have some errors, but got no errors.
+`,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have no errors, but got ${errors.length} error(s).
+      `,
+      { errors: [] },
+      { errors },
+      true
+    );
+
+    utils.flag(this, 'object', errors);
+  });
+
+  Assertion.addMethod('errorAtIndex', function(index) {
+    const { errors } = this._obj;
+    const errorsCount = errors.length;
+
+    new Assertion(errors).to.be.instanceOf(Array);
+    new Assertion(errorsCount).to.be.a('number');
+
+    this.assert(
+      errors[index],
+      `Expected to have error at index ${index}`,
+      `Expected NOT to have error at index ${index}`
+    );
+
+    utils.flag(this, 'currentError', errors[index]);
+    utils.flag(this, 'currentErrorIndex', index);
+  });
+
+  Assertion.addMethod('validator', function(expectedValue) {
+    const { validator: actualValue } = this._obj;
+    const stringifiedObj = stringify(this._obj);
+
+    this.assert(
+      actualValue === expectedValue,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have "${expectedValue}" validator, but got "${actualValue}".
+      `,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to not have validator equal to "${expectedValue}".
+`,
+      expectedValue,
+      actualValue,
+      true
+    );
+  });
+
+  Assertion.addMethod('expectedType', function(expectedValue) {
+    const { expectedType: actualValue } = this._obj;
+    const stringifiedObj = stringify(this._obj);
+
+    this.assert(
+      actualValue === expectedValue,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have an "expectedType" equal to "${expectedValue}", but got "${actualValue}".
+  `,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to not have an "expectedType" of "${expectedValue}".
+      `,
+      expectedValue,
+      actualValue,
+      true
+    );
+  });
+
+  Assertion.addMethod('realType', function(expectedValue) {
+    const { realType: actualValue } = this._obj;
+    const stringifiedObj = stringify(this._obj);
+
+    this.assert(
+      actualValue === expectedValue,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to have an "realType" equal to "${expectedValue}", but got "${actualValue}".
+`,
+      `
+Expected the following HTTP message field:
+
+${stringifiedObj}
+
+to not have an "realType" of "${expectedValue}".
+      `,
+      expectedValue,
+      actualValue,
+      true
+    );
+  });
+});
+
+module.exports = chai;