[docs] Added Testing instructions in Contributing.md

Co-authored-by: Puja Jagani <[email protected]>

CONTRIBUTING.md

@@ -180,7 +180,106 @@ Use `git rebase` (not `git merge`) to sync your work from time to time.
 ### Step 5: Test
 
 Bug fixes and features **should have tests**. Look at other tests to
-see how they should be structured.
+see how they should be structured. Verify that new and existing tests are 
+passing locally before pushing code.
+
+#### Running tests locally
+
+Build your code for the latest changes and run tests locally.
+
+##### Python
+<details>
+ <summary>
+ Click to see How to run Python Tests.
+ </summary>
+
+ It's not mandatory to run tests sequentially but running Unit tests
+ before browser testing is recommended.
+
+ Unit Tests
+ ```shell
+ % bazel test //py:unit
+ ```
+
+ Remote Tests
+ ```shell
+ % bazel test --jobs 1 //py:test-remote
+ ```
+
+ Browser Tests
+ ```shell
+ % bazel test //py:test-<browsername> #eg test-chrome, test-firefox
+ ```
+</details>
+
+##### Javascript
+<details>
+ <summary>
+ Click to see How to run JavaScript Tests.
+ </summary>
+
+ Node Tests
+ ```shell
+ % bazel test //javascript/node/selenium-webdriver:tests
+ ```
+
+ Firefox Atom Tests
+ ```shell
+ % bazel test --test_tag_filters=firefox //javascript/atoms/... //javascript/selenium-atoms/... //javascript/webdriver/...
+ ```
+
+ Grid UI Unit Tests
+ ```shell
+ % cd javascript/grid-ui && npm install && npm test
+ ```
+</details>
+
+##### Java
+<details>
+ <summary>
+ Click to see How to run Java Tests.
+ </summary>
+
+ Small Tests
+ ```shell
+ % bazel test --cache_test_results=no --test_size_filters=small grid java/test/...
+ ```
+
+ Large Tests
+ ```shell
+ % bazel test --cache_test_results=no java/test/org/openqa/selenium/grid/router:large-tests
+ ```
+
+ Browser Tests
+ ```shell
+ bazel test --test_size_filters=small,medium --cache_test_results=no --test_tag_filters=-browser-test //java/...
+ ```
+</details>
+
+##### Ruby
+<details>
+ <summary>
+ Click to see How to run Ruby Tests.
+ </summary>
+
+ It's not mandatory to run tests sequentially but running Unit tests
+ before browser testing is recommended.
+ 
+ Unit Tests
+ ```shell
+ % bazel test rb:unit-test
+ ```
+
+ Chrome Tests
+ ```shell
+ bazel test rb:chrome-test
+ ```
+
+ Remote Tests
+ ```shell
+ % bazel test --test_output=all --test_arg="-tfocus" --test_arg="--fail-fast" rb:remote-chrome-test
+ ```
+</details>
 
 ### Step 6: Push