new file mode 100644
--- /dev/null
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_install_file_change.js
@@ -0,0 +1,176 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+"use strict";
+
+const server = AddonTestUtils.createHttpServer({ hosts: ["example.com"] });
+
+// The test extension uses an insecure update url.
+Services.prefs.setBoolPref("extensions.checkUpdateSecurity", false);
+
+/* globals browser */
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+async function createXPIWithID(addonId, version = "1.0") {
+  let xpiFile = await createTempWebExtensionFile({
+    manifest: {
+      version,
+      applications: { gecko: { id: addonId } },
+    },
+  });
+  return xpiFile;
+}
+
+const ERROR_PATTERN_INSTALL_FAIL = /Failed to install .+ from .+ to /;
+const ERROR_PATTERN_POSTPONE_FAIL = /Failed to postpone install of /;
+
+async function promiseInstallFail(install, expectedErrorPattern) {
+  let { messages } = await promiseConsoleOutput(async () => {
+    await Assert.rejects(
+      install.install(),
+      /^Error: Install failed: onInstallFailed$/
+    );
+  });
+  messages = messages.filter(msg => expectedErrorPattern.test(msg.message));
+  equal(messages.length, 1, "Expected log messages");
+  equal(install.state, AddonManager.STATE_INSTALL_FAILED);
+  equal(install.error, AddonManager.ERROR_FILE_ACCESS);
+  equal((await AddonManager.getAllInstalls()).length, 0, "no pending installs");
+}
+
+add_task(async function test_file_deleted() {
+  let xpiFile = await createXPIWithID("delete@me");
+  let install = await AddonManager.getInstallForFile(xpiFile);
+  equal(install.state, AddonManager.STATE_DOWNLOADED);
+
+  xpiFile.remove(false);
+
+  await promiseInstallFail(install, ERROR_PATTERN_INSTALL_FAIL);
+
+  equal(await AddonManager.getAddonByID("delete@me"), null);
+});
+
+add_task(async function test_file_emptied() {
+  let xpiFile = await createXPIWithID("empty@me");
+  let install = await AddonManager.getInstallForFile(xpiFile);
+  equal(install.state, AddonManager.STATE_DOWNLOADED);
+
+  await IOUtils.write(xpiFile.path, new Uint8Array());
+
+  await promiseInstallFail(install, ERROR_PATTERN_INSTALL_FAIL);
+
+  equal(await AddonManager.getAddonByID("empty@me"), null);
+});
+
+add_task(async function test_file_replaced() {
+  let xpiFile = await createXPIWithID("replace@me");
+  let install = await AddonManager.getInstallForFile(xpiFile);
+  equal(install.state, AddonManager.STATE_DOWNLOADED);
+
+  await IOUtils.copy(
+    (await createXPIWithID("replace@me", "2")).path,
+    xpiFile.path
+  );
+
+  await promiseInstallFail(install, ERROR_PATTERN_INSTALL_FAIL);
+
+  equal(await AddonManager.getAddonByID("replace@me"), null);
+});
+
+async function do_test_update_with_file_replaced(wantPostponeTest) {
+  const ADDON_ID = wantPostponeTest ? "postpone@me" : "update@me";
+  function backgroundWithPostpone() {
+    // The registration of this listener postpones the update.
+    browser.runtime.onUpdateAvailable.addListener(() => {
+      browser.test.fail("Unusable update should not call onUpdateAvailable");
+    });
+  }
+  await promiseInstallWebExtension({
+    manifest: {
+      version: "1.0",
+      applications: {
+        gecko: {
+          id: ADDON_ID,
+          update_url: `http://example.com/update-${ADDON_ID}.json`,
+        },
+      },
+    },
+    background: wantPostponeTest ? backgroundWithPostpone : () => {},
+  });
+
+  server.registerFile(
+    `/update-${ADDON_ID}.xpi`,
+    await createTempWebExtensionFile({
+      manifest: {
+        version: "2.0",
+        applications: { gecko: { id: ADDON_ID } },
+      },
+    })
+  );
+  AddonTestUtils.registerJSON(server, `/update-${ADDON_ID}.json`, {
+    addons: {
+      [ADDON_ID]: {
+        updates: [
+          {
+            version: "2.0",
+            update_link: `http://example.com/update-${ADDON_ID}.xpi`,
+          },
+        ],
+      },
+    },
+  });
+
+  // Setup completed, let's try to verify that file corruption halts the update.
+
+  let addon = await promiseAddonByID(ADDON_ID);
+  equal(addon.version, "1.0");
+
+  let update = await promiseFindAddonUpdates(
+    addon,
+    AddonManager.UPDATE_WHEN_USER_REQUESTED
+  );
+  let install = update.updateAvailable;
+  equal(install.version, "2.0");
+  equal(install.state, AddonManager.STATE_AVAILABLE);
+  equal(install.existingAddon, addon);
+  equal(install.file, null);
+
+  let promptCount = 0;
+  let didReplaceFile = false;
+  install.promptHandler = async function() {
+    ++promptCount;
+    equal(install.state, AddonManager.STATE_DOWNLOADED);
+    await IOUtils.copy(
+      (await createXPIWithID(ADDON_ID, "3")).path,
+      install.file.path
+    );
+    didReplaceFile = true;
+    equal(install.state, AddonManager.STATE_DOWNLOADED, "State not changed");
+  };
+
+  if (wantPostponeTest) {
+    await promiseInstallFail(install, ERROR_PATTERN_POSTPONE_FAIL);
+  } else {
+    await promiseInstallFail(install, ERROR_PATTERN_INSTALL_FAIL);
+  }
+
+  equal(promptCount, 1);
+  ok(didReplaceFile, "Replaced update with different file");
+
+  // Now verify that the add-on is still at the old version.
+  addon = await promiseAddonByID(ADDON_ID);
+  equal(addon.version, "1.0");
+
+  await addon.uninstall();
+}
+
+add_task(async function test_update_and_file_replaced() {
+  await do_test_update_with_file_replaced();
+});
+
+add_task(async function test_update_postponed_and_file_replaced() {
+  await do_test_update_with_file_replaced(/* wantPostponeTest = */ true);
+});

--- a/toolkit/mozapps/extensions/test/xpcshell/xpcshell.ini
+++ b/toolkit/mozapps/extensions/test/xpcshell/xpcshell.ini
@@ -48,16 +48,17 @@ tags = webextensions
 [test_getInstallSourceFromHost.js]
 [test_gmpProvider.js]
 skip-if = appname != "firefox" || (os == "win" && processor == "aarch64") # bug 1536637
 [test_harness.js]
 [test_hidden.js]
 [test_install.js]
 [test_installOrigins.js]
 [test_install_cancel.js]
+[test_install_file_change.js]
 [test_install_icons.js]
 [test_installtrigger_schemes.js]
 [test_installtrigger_deprecation.js]
 [test_isDebuggable.js]
 [test_isReady.js]
 [test_loadManifest_isPrivileged.js]
 [test_locale.js]
 [test_moved_extension_metadata.js]