diff --git a/build/azure-pipelines/darwin/continuous-build-darwin.yml b/build/azure-pipelines/darwin/continuous-build-darwin.yml
index c8f5b08fe2a..ccf32d1ded7 100644
--- a/build/azure-pipelines/darwin/continuous-build-darwin.yml
+++ b/build/azure-pipelines/darwin/continuous-build-darwin.yml
@@ -42,7 +42,7 @@ steps:
     ./scripts/test.sh --tfs "Unit Tests"
   displayName: Run Unit Tests (Electron)
 - script: |
-    yarn test-browser --browser chromium --browser webkit
+    yarn test-browser --browser chromium --browser webkit --browser firefox
   displayName: Run Unit Tests (Browser)
 - script: |
     ./scripts/test-integration.sh --tfs "Integration Tests"
diff --git a/build/azure-pipelines/darwin/product-build-darwin.yml b/build/azure-pipelines/darwin/product-build-darwin.yml
index d77dbbd2e0f..8a066685166 100644
--- a/build/azure-pipelines/darwin/product-build-darwin.yml
+++ b/build/azure-pipelines/darwin/product-build-darwin.yml
@@ -118,7 +118,7 @@ steps:
 
 - script: |
     set -e
-    yarn test-browser --build --browser chromium --browser webkit
+    yarn test-browser --build --browser chromium --browser webkit --browser firefox
   displayName: Run unit tests (Browser)
   condition: and(succeeded(), eq(variables['VSCODE_STEP_ON_IT'], 'false'))
 
diff --git a/build/azure-pipelines/linux/continuous-build-linux.yml b/build/azure-pipelines/linux/continuous-build-linux.yml
index 9de15845c04..9c62cbd8d7c 100644
--- a/build/azure-pipelines/linux/continuous-build-linux.yml
+++ b/build/azure-pipelines/linux/continuous-build-linux.yml
@@ -50,7 +50,7 @@ steps:
     DISPLAY=:10 ./scripts/test.sh --tfs "Unit Tests"
   displayName: Run Unit Tests (Electron)
 - script: |
-    DISPLAY=:10 yarn test-browser --browser chromium
+    DISPLAY=:10 yarn test-browser --browser chromium --browser firefox
   displayName: Run Unit Tests (Browser)
 - script: |
     DISPLAY=:10 ./scripts/test-integration.sh --tfs "Integration Tests"
diff --git a/build/azure-pipelines/linux/product-build-linux.yml b/build/azure-pipelines/linux/product-build-linux.yml
index 119f80cd929..cc703eed8f5 100644
--- a/build/azure-pipelines/linux/product-build-linux.yml
+++ b/build/azure-pipelines/linux/product-build-linux.yml
@@ -123,7 +123,7 @@ steps:
 
 - script: |
     set -e
-    DISPLAY=:10 yarn test-browser --build --browser chromium
+    DISPLAY=:10 yarn test-browser --build --browser chromium --browser firefox
   displayName: Run unit tests (Browser)
   condition: and(succeeded(), eq(variables['VSCODE_STEP_ON_IT'], 'false'))
 
diff --git a/build/azure-pipelines/win32/continuous-build-win32.yml b/build/azure-pipelines/win32/continuous-build-win32.yml
index e438550f8f5..a0a6aaa2e46 100644
--- a/build/azure-pipelines/win32/continuous-build-win32.yml
+++ b/build/azure-pipelines/win32/continuous-build-win32.yml
@@ -47,7 +47,7 @@ steps:
     .\scripts\test.bat --tfs "Unit Tests"
   displayName: Run Unit Tests (Electron)
 - powershell: |
-    yarn test-browser --browser chromium
+    yarn test-browser --browser chromium --browser firefox
   displayName: Run Unit Tests (Browser)
 - powershell: |
     .\scripts\test-integration.bat --tfs "Integration Tests"
diff --git a/build/azure-pipelines/win32/product-build-win32.yml b/build/azure-pipelines/win32/product-build-win32.yml
index 20699bf9225..4d667a4ad1b 100644
--- a/build/azure-pipelines/win32/product-build-win32.yml
+++ b/build/azure-pipelines/win32/product-build-win32.yml
@@ -132,7 +132,7 @@ steps:
 - powershell: |
     . build/azure-pipelines/win32/exec.ps1
     $ErrorActionPreference = "Stop"
-    exec { yarn test-browser --build --browser chromium }
+    exec { yarn test-browser --build --browser chromium --browser firefox }
   displayName: Run unit tests (Browser)
   condition: and(succeeded(), eq(variables['VSCODE_STEP_ON_IT'], 'false'))