From b02325ae2f70cfef1615431a9c78d0a7839c3091 Mon Sep 17 00:00:00 2001
From: Rogelio Guzman <rogelioguzmanh@gmail.com>
Date: Tue, 15 Aug 2017 18:55:20 -0700
Subject: [PATCH] Make toBe matcher error message more helpful for objects and
 arrays

---
 .../__snapshots__/matchers.test.js.snap       | 27 +++----------------
 packages/jest-matchers/src/matchers.js        | 12 +++++++++
 2 files changed, 15 insertions(+), 24 deletions(-)

diff --git a/packages/jest-matchers/src/__tests__/__snapshots__/matchers.test.js.snap b/packages/jest-matchers/src/__tests__/__snapshots__/matchers.test.js.snap
index 238a0944159f..ce84c22a733e 100644
--- a/packages/jest-matchers/src/__tests__/__snapshots__/matchers.test.js.snap
+++ b/packages/jest-matchers/src/__tests__/__snapshots__/matchers.test.js.snap
@@ -232,27 +232,13 @@ Received:
 exports[`.toBe() fails for: [] and [] 1`] = `
 "<dim>expect(<red>received</><dim>).toBe(<green>expected</><dim>)
 
-Expected value to be (using ===):
-  <green>[]</>
-Received:
-  <red>[]</>
-
-Difference:
-
-<dim>Compared values have no visual difference."
+Looks like you wanted to test for object/array equity with strict \`toBe\` matcher. You probably need to use \`toEqual\` instead."
 `;
 
 exports[`.toBe() fails for: {"a": 1} and {"a": 1} 1`] = `
 "<dim>expect(<red>received</><dim>).toBe(<green>expected</><dim>)
 
-Expected value to be (using ===):
-  <green>{\\"a\\": 1}</>
-Received:
-  <red>{\\"a\\": 1}</>
-
-Difference:
-
-<dim>Compared values have no visual difference."
+Looks like you wanted to test for object/array equity with strict \`toBe\` matcher. You probably need to use \`toEqual\` instead."
 `;
 
 exports[`.toBe() fails for: {"a": 1} and {"a": 5} 1`] = `
@@ -277,14 +263,7 @@ Difference:
 exports[`.toBe() fails for: {} and {} 1`] = `
 "<dim>expect(<red>received</><dim>).toBe(<green>expected</><dim>)
 
-Expected value to be (using ===):
-  <green>{}</>
-Received:
-  <red>{}</>
-
-Difference:
-
-<dim>Compared values have no visual difference."
+Looks like you wanted to test for object/array equity with strict \`toBe\` matcher. You probably need to use \`toEqual\` instead."
 `;
 
 exports[`.toBe() fails for: 1 and 2 1`] = `
diff --git a/packages/jest-matchers/src/matchers.js b/packages/jest-matchers/src/matchers.js
index 443671603946..9ae4f5b6c3d7 100644
--- a/packages/jest-matchers/src/matchers.js
+++ b/packages/jest-matchers/src/matchers.js
@@ -67,6 +67,18 @@ const matchers: MatchersObject = {
           `Received:\n` +
           `  ${printReceived(received)}`
       : () => {
+          if (
+            getType(received) === getType(expected) &&
+            (getType(received) === 'object' || getType(expected) === 'array') &&
+            equals(received, expected, [iterableEquality])
+          ) {
+            return (
+              matcherHint('.toBe') +
+              '\n\n' +
+              'Looks like you wanted to test for object/array equity with strict `toBe` matcher. You probably need to use `toEqual` instead.'
+            );
+          }
+
           const diffString = diff(expected, received, {
             expand: this.expand,
           });