test-link: add stringification to equality check

Changelog.md

@@ -13,6 +13,9 @@
 - The result of a mutation is now made available to the wrapped component, 
   when using the `graphql` HOC.  <br/>
   [@andycarrell](https://github.com/andycarrell) in [#3008](https://github.com/apollographql/react-apollo/pull/3008) 
+- Check equality of stringified variables in the `MockLink` to improve
+  debugging experience used by `MockedProvider`.  <br/>
+  [@evans](https://github.com/evans) in [#3078](https://github.com/apollographql/react-apollo/pull/3078)
 
 ### Bug Fixes
 

package.json

@@ -109,6 +109,7 @@
   "devDependencies": {
     "@types/enzyme": "3.9.3",
     "@types/enzyme-adapter-react-16": "1.0.5",
+    "@types/fast-json-stable-stringify": "^2.0.0",
     "@types/graphql": "14.2.0",
     "@types/hoist-non-react-statics": "3.3.1",
     "@types/invariant": "2.2.29",
@@ -165,6 +166,7 @@
   },
   "dependencies": {
     "apollo-utilities": "^1.3.0",
+    "fast-json-stable-stringify": "^2.0.0",
     "hoist-non-react-statics": "^3.3.0",
     "lodash.isequal": "^4.5.0",
     "prop-types": "^15.7.2",

src/test-links.ts

@@ -6,6 +6,7 @@ import {
   Observable,
   // Observer,
 } from 'apollo-link';
+import stringify from 'fast-json-stable-stringify';
 
 import { print } from 'graphql/language/printer';
 import {
@@ -67,7 +68,7 @@ export class MockLink extends ApolloLink {
     const response = (this.mockedResponsesByKey[key] || []).find((res, index) => {
       const requestVariables = operation.variables || {};
       const mockedResponseVariables = res.request.variables || {};
-      if (!isEqual(requestVariables, mockedResponseVariables)) {
+      if (!isEqual(stringify(requestVariables), stringify(mockedResponseVariables))) {
         return false;
       }
       responseIndex = index;