diff --git a/Contributing.md b/Contributing.md
index 9a80573..334c68c 100644
--- a/Contributing.md
+++ b/Contributing.md
@@ -82,11 +82,12 @@ Now you have automatic linting of your changes to JavaScript files whenever you
 
 **Run testing**
 
-To ensure that your changes did not introduce any regressions you need to run the testing framework. We have three different kinds of tests:
+To ensure that your changes did not introduce any regressions you need to run the testing framework. We have four different kinds of tests:
 
-* Unit tests (ensure that individual units of code work as expected)
+* Unit tests (ensures that individual units of code work as expected)
 * Font tests (special kind of unit tests that use `ttx` for font validation)
-* Browser tests (screenshot testing of rendered PDF files in the browser)
+* Integration tests (automated viewer tests)
+* Reference tests (screenshot testing of rendered PDF files in the browser)
 
 The browser tests are split into the following types of tests:
 
@@ -94,7 +95,9 @@ The browser tests are split into the following types of tests:
 * `eq` test (reference test that takes correctly rendered snapshots and compares them to snapshots from the current code)
 * `text` test (reference test that takes snapshots of the text layer overlay and compares them to snapshots from the current code)
 * `annotations` test (reference test that takes snapshots of the annotation layer overlay and compares them to snapshots from the current code)
-* `fbf` test (forward-back-forward test)
+* `fbf` test (forward-back-forward page scrolling test)
+
+Finally, check the impact on code coverage too; see https://github.com/mozilla/pdf.js#code-coverage for more information. It's important that changes are covered by tests where possible.
 
 **Generating reference images**