diff --git a/addons/xterm-addon-fit/src/FitAddon.api.ts b/addons/xterm-addon-fit/src/FitAddon.api.ts
index 760a31761f..798b2fc54a 100644
--- a/addons/xterm-addon-fit/src/FitAddon.api.ts
+++ b/addons/xterm-addon-fit/src/FitAddon.api.ts
@@ -14,8 +14,6 @@ let page: Page;
 const width = 1024;
 const height = 768;
 
-let isFirefox = false;
-
 describe('FitAddon', () => {
   before(async function(): Promise<any> {
     const browserType = getBrowserType();
@@ -27,10 +25,6 @@ describe('FitAddon', () => {
     await page.setViewportSize({ width, height });
     await page.goto(APP);
     await openTerminal(page);
-    // This is used to do conditional assertions since cell height is 1 pixel higher with the
-    // default font on Firefox. Minor differences in font rendering/sizing is expected so this is
-    // fine.
-    isFirefox = await page.evaluate(`navigator.userAgent.toLowerCase().indexOf('firefox') > -1`);
   });
 
   after(async () => {
@@ -49,18 +43,18 @@ describe('FitAddon', () => {
 
     it('default', async function(): Promise<any> {
       await loadFit();
-      assert.deepEqual(await page.evaluate(`window.fit.proposeDimensions()`), {
-        cols: 87,
-        rows: isFirefox ? 28 : 26
-      });
+      const dimensions: {cols: number, rows: number} = await page.evaluate(`window.fit.proposeDimensions()`);
+      assert.equal(dimensions.cols, 87);
+      assert.isAbove(dimensions.rows, 24);
+      assert.isBelow(dimensions.rows, 29);
     });
 
     it('width', async function(): Promise<any> {
       await loadFit(1008);
-      assert.deepEqual(await page.evaluate(`window.fit.proposeDimensions()`), {
-        cols: 110,
-        rows: isFirefox ? 28 : 26
-      });
+      const dimensions: {cols: number, rows: number} = await page.evaluate(`window.fit.proposeDimensions()`);
+      assert.equal(dimensions.cols, 110);
+      assert.isAbove(dimensions.rows, 24);
+      assert.isBelow(dimensions.rows, 29);
     });
 
     it('small', async function(): Promise<any> {
@@ -80,15 +74,21 @@ describe('FitAddon', () => {
     it('default', async function(): Promise<any> {
       await loadFit();
       await page.evaluate(`window.fit.fit()`);
-      assert.equal(await page.evaluate(`window.term.cols`), 87);
-      assert.equal(await page.evaluate(`window.term.rows`), isFirefox ? 28 : 26);
+      const cols: number = await page.evaluate(`window.term.cols`);
+      const rows: number = await page.evaluate(`window.term.rows`);
+      assert.equal(cols, 87);
+      assert.isAbove(rows, 24);
+      assert.isBelow(rows, 29);
     });
 
     it('width', async function(): Promise<any> {
       await loadFit(1008);
       await page.evaluate(`window.fit.fit()`);
-      assert.equal(await page.evaluate(`window.term.cols`), 110);
-      assert.equal(await page.evaluate(`window.term.rows`), isFirefox ? 28 : 26);
+      const cols: number = await page.evaluate(`window.term.cols`);
+      const rows: number = await page.evaluate(`window.term.rows`);
+      assert.equal(cols, 110);
+      assert.isAbove(rows, 24);
+      assert.isBelow(rows, 29);
     });
 
     it('small', async function(): Promise<any> {
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 7f8d36fb7e..adeecb88b7 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -6,7 +6,7 @@
 jobs:
 - job: Linux
   pool:
-    vmImage: 'ubuntu-16.04'
+    vmImage: 'ubuntu-18.04'
   steps:
   - task: NodeTool@0
     inputs:
@@ -79,8 +79,12 @@ jobs:
 
 - job: Linux_IntegrationTests
   pool:
-    vmImage: 'ubuntu-16.04'
+    vmImage: 'ubuntu-18.04'
   steps:
+  - script: |
+      sudo apt update
+      sudo apt install libwoff1 libopus0 libwebp6 libwebpdemux2 libenchant1c2a libgudev-1.0-0 libsecret-1-0 libhyphen0 libgdk-pixbuf2.0-0 libegl1 libgles2 libevent-2.1-6 libnotify4 libxslt1.1
+    displayName: Install required packages
   - task: NodeTool@0
     inputs:
       versionSpec: '10.x'
@@ -102,6 +106,8 @@ jobs:
     displayName: 'Start test server'
   - script: yarn test-api-chromium --headless --forbid-only
     displayName: 'Integration tests (Chromium)'
+  - script: xvfb-run --auto-servernum -- bash -c "yarn test-api-firefox --headless --forbid-only"
+    displayName: 'Integration tests (Firefox)'
 
 - job: macOS_IntegrationTests
   pool: