From 091b4d3701ad5957cfaf0283e111557c6a323a6c Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Thu, 10 May 2018 19:36:01 -0500
Subject: [PATCH] Add Turn Off Console Error Messages In A Test as a javascript
 til

---
 README.md                                     |  3 ++-
 ...rn-off-console-error-messages-in-a-test.md | 25 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 javascript/turn-off-console-error-messages-in-a-test.md

diff --git a/README.md b/README.md
index c315fa0..679b460 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_677 TILs and counting..._
+_678 TILs and counting..._
 
 ---
 
@@ -268,6 +268,7 @@ _677 TILs and counting..._
 - [Timing Processes](javascript/timing-processes.md)
 - [Transforming ES6 and JSX With Babel 6](javascript/transforming-es6-and-jsx-with-babel-6.md)
 - [Truthiness of Integer Arrays](javascript/truthiness-of-integer-arrays.md)
+- [Turn Off Console Error Messages In A Test](javascript/turn-off-console-error-messages-in-a-test.md)
 - [Waiting On Multiple Promises](javascript/waiting-on-multiple-promises.md)
 - [Who Am I: NPM Edition](javascript/who-am-i-npm-edition.md)
 - [Yarn Commands Without The Emojis](javascript/yarn-commands-without-the-emojis.md)
diff --git a/javascript/turn-off-console-error-messages-in-a-test.md b/javascript/turn-off-console-error-messages-in-a-test.md
new file mode 100644
index 0000000..90c4d90
--- /dev/null
+++ b/javascript/turn-off-console-error-messages-in-a-test.md
@@ -0,0 +1,25 @@
+# Turn Off Console Error Messages In A Test
+
+I'm using [Jest](https://facebook.github.io/jest/) to test a React component
+that requires a prop via
+[PropTypes](https://reactjs.org/docs/typechecking-with-proptypes.html). In
+one of my tests, I want to test that component when the required prop is
+excluded. The side effect of doing this is that my test output gets
+cluttered with the PropType warning.
+
+The thing to do is silence the error message during that test.
+
+```javascript
+it('renders a component without a required prop', () => {
+  const originalError = console.error;
+  console.error = jest.fn();
+
+  // test code here
+  expect(shallow(<My Component />)).toDoSomething;
+
+  console.error = originalError;
+});
+```
+
+We can silence `console.error` by temporarily replacing it with a
+Jest-mocked function and then putting it back at the end of the test.