diff --git a/scripts/run_changed.js b/scripts/run_changed.js
index 7c5f2f05090..c476391c3e2 100644
--- a/scripts/run_changed.js
+++ b/scripts/run_changed.js
@@ -16,7 +16,7 @@
  */
 
 const { resolve } = require('path');
-const { spawn } = require('child-process-promise');
+const { spawn, exec } = require('child-process-promise');
 const chalk = require('chalk');
 const simpleGit = require('simple-git/promise');
 
@@ -52,35 +52,84 @@ const alwaysRunTestPaths = [
   'integration/webpack'
 ];
 
+/**
+ * These files trigger tests in other dirs
+ */
+const specialPaths = {
+  'scripts/emulator-testing/emulators/firestore-emulator.ts': ['packages/firestore'],
+  'scripts/emulator-testing/emulators/database-emulator.ts': ['packages/database'],
+  'scripts/emulator-testing/emulators/emulator.ts': ['packages/firestore', 'packages/database'],
+  'scripts/emulator-testing/firestore-test-runner.ts': ['packages/firestore'],
+  'scripts/emulator-testing/database-test-runner.ts': ['packages/database']
+};
+
 /**
  * Identify modified packages that require tests.
  */
 async function getChangedPackages() {
+  const packageInfo = JSON.parse(
+    (await exec('npx lerna ls --json', { cwd: root })).stdout
+  );
+  const depGraph = JSON.parse(
+    (await exec('npx lerna ls --graph', { cwd: root })).stdout
+  );
   const diff = await git.diff(['--name-only', 'origin/master...HEAD']);
   const changedFiles = diff.split('\n');
   const changedPackages = {};
   for (const filename of changedFiles) {
+    // Files that trigger full test suite.
     if (fullTestTriggerFiles.includes(filename)) {
       console.log(
         chalk`{blue Running all tests because ${filename} was modified.}`
       );
       return { testAll: true };
     }
+    // Files outside a package dir that should trigger its tests.
+    if (specialPaths[filename]) {
+      for (const targetPackage of specialPaths[filename]) {
+        changedPackages[targetPackage] = 'dependency';
+      }
+    }
+    // Check for changed files inside package dirs.
     const match = filename.match('^(packages/[a-zA-Z0-9-]+)/.*');
     if (match && match[1]) {
-      const pkg = require(resolve(root, match[1], 'package.json'));
-      if (pkg && pkg.scripts.test) {
-        changedPackages[match[1]] = true;
+      const changedPackage = require(resolve(root, match[1], 'package.json'));
+      if (changedPackage) {
+        if (changedPackage.scripts.test) {
+          // Add the package itself.
+          changedPackages[match[1]] = 'direct';
+        }
+        // Add packages that depend on it.
+        for (const package in depGraph) {
+          if (depGraph[package].includes(changedPackage.name)) {
+            const depData = packageInfo.find(item => item.name === package);
+            if (depData) {
+              const depPkgJson = require(resolve(
+                depData.location,
+                'package.json'
+              ));
+              if (depPkgJson && depPkgJson.scripts.test) {
+                const depPath = depData.location.replace(`${root}/`, '');
+                if (!changedPackages[depPath]) {
+                  changedPackages[depPath] = 'dependency';
+                }
+              }
+            }
+          }
+        }
       }
     }
   }
   if (Object.keys(changedPackages).length > 0) {
-    return { testAll: false, packageDirs: Object.keys(changedPackages) };
+    return {
+      testAll: false,
+      changedPackages
+    };
   } else {
     console.log(
       chalk`{green No changes detected in any package. Skipping all package-specific tests.}`
     );
-    return { testAll: false, packageDirs: [] };
+    return { testAll: false };
   }
 }
 
@@ -103,21 +152,28 @@ async function runTests(pathList) {
 
 async function main() {
   try {
-    const { testAll, packageDirs = [] } = await getChangedPackages();
+    const {
+      testAll,
+      changedPackages = {}
+    } = await getChangedPackages();
     if (testAll) {
       await spawn('yarn', ['test'], {
         stdio: 'inherit'
       });
     } else {
       console.log(chalk`{blue Running tests in:}`);
-      for (const filename of alwaysRunTestPaths) {
+      for (const filename of alwaysRunTestPaths) { // array
         console.log(chalk`{green ${filename} (always runs)}`);
       }
-      for (const filename of packageDirs) {
-        console.log(chalk`{yellow ${filename} (contains modified files)}`);
+      for (const filename in changedPackages) { // obj
+        if (changedPackages[filename] === 'direct') {
+          console.log(chalk`{yellow ${filename} (contains modified files)}`);
+        } else {
+          console.log(chalk`{yellow ${filename} (depends on modified files)}`);
+        }
       }
       await runTests(alwaysRunTestPaths);
-      await runTests(packageDirs);
+      await runTests(Object.keys(changedPackages));
     }
   } catch (e) {
     console.error(e);