🔀 Applied changes from alex-cannon pr jestjs#9109

.dockerignore

@@ -0,0 +1,3 @@
+# Reference: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Exclude node_modules
+node_modules

CHANGELOG.md

@@ -13,6 +13,8 @@
 ### Chore & Maintenance
 
 - `[*]` Replace internal usage of `pretty-format/ConvertAnsi` with `jest-serializer-ansi-escapes` ([#12935](https://github.com/facebook/jest/pull/12935), [#13004](https://github.com/facebook/jest/pull/13004))
+- `[*]` Added Dockerfile for Jest Development ([#9109](https://github.com/facebook/jest/pull/9109))
+
 
 ### Performance
 

CONTRIBUTING.md

@@ -33,6 +33,28 @@ _Before_ submitting a pull request, please make sure the following is done…
     ```
 
     Note: Replace `<your_username>` with your GitHub username
+1.  Run Jest with [Docker](https://docs.docker.com/engine/docker-overview/) (Optional) or continue reading for manual instructions.
+
+    1. If you haven't already, [Install Docker](https://docs.docker.com/install/).
+
+    1. Navigate to the `/jest` directory. You should be able to see the `Dockerfile` file when you run `ls`.
+
+    1. Build the Jest image (may take a few minutes):
+
+    ```sh
+    docker build -t jest .
+    ```
+
+    1. Run the Jest image:
+
+    ```sh
+    docker run --volume="YOUR_PATH_TO_JEST:/usr/src/app" --rm jest:latest
+    ```
+
+    1. The `yarn run watch` command will watch the `/packages` directory for file changes. See `package.json` for a full list of commands. [Learn how to run commands in a container](https://docs.docker.com/engine/reference/commandline/exec/) or visit the [official Docker docs](https://docs.docker.com/) for other Docker related questions.
+
+    1. **Skip to step #8 and continue reading.**
+
 
 1.  Jest uses [Yarn](https://code.facebook.com/posts/1840075619545360) for running development scripts. If you haven't already done so, please [install yarn](https://yarnpkg.com/en/docs/install).
 

Dockerfile

@@ -0,0 +1,24 @@
+#Build: docker build -t jest .
+#Run: docker run --volume="$PWD:/usr/src/app" --rm jest:latest
+
+#Use Node 12.13.0 image
+#Includes Python2.7
+FROM node:12
+
+#Setup basic environment
+ENV DEBIAN_FRONTEND=noninteractive \
+    LANG=en_US.UTF-8 \
+    LC_ALL=C.UTF-8 \
+    LANGUAGE=en_US.UTF-8
+
+WORKDIR /usr/src/app
+
+#Copy entire directory
+COPY . ./
+
+#Install dependencies
+RUN yarn
+
+#Build && Watch for changes
+ENTRYPOINT ["yarn"]
+CMD ["watch"]