--- a/mobile/android/base/java/org/mozilla/gecko/db/BrowserDatabaseHelper.java
+++ b/mobile/android/base/java/org/mozilla/gecko/db/BrowserDatabaseHelper.java
@@ -13,16 +13,17 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
 import org.mozilla.apache.commons.codec.binary.Base32;
 import org.mozilla.gecko.GeckoProfile;
 import org.mozilla.gecko.R;
 import org.mozilla.gecko.Telemetry;
+import org.mozilla.gecko.annotation.RobocopTarget;
 import org.mozilla.gecko.db.BrowserContract.Bookmarks;
 import org.mozilla.gecko.db.BrowserContract.Combined;
 import org.mozilla.gecko.db.BrowserContract.Favicons;
 import org.mozilla.gecko.db.BrowserContract.History;
 import org.mozilla.gecko.db.BrowserContract.Numbers;
 import org.mozilla.gecko.db.BrowserContract.ReadingListItems;
 import org.mozilla.gecko.db.BrowserContract.SearchHistory;
 import org.mozilla.gecko.db.BrowserContract.Thumbnails;
@@ -1162,17 +1163,19 @@ public final class BrowserDatabaseHelper
         createLoginsTable(db, TABLE_LOGINS);
         createLoginsTableIndices(db, TABLE_LOGINS);
     }
 
     // Get the cache path for a URL, based on the storage format in place during the 27to28 transition.
     // This is a reimplementation of _toHashedPath from ReaderMode.jsm - given that we're likely
     // to migrate the SavedReaderViewHelper implementation at some point, it seems safest to have a local
     // implementation here - moreover this is probably faster than calling into JS.
-    private static String getReaderCacheFileNameForURL(String url) {
+    // This is public only to allow for testing.
+    @RobocopTarget
+    public static String getReaderCacheFileNameForURL(String url) {
         try {
             // On KitKat and above we can use java.nio.charset.StandardCharsets.UTF_8 in place of "UTF8"
             // which avoids having to handle UnsupportedCodingException
             byte[] utf8 = url.getBytes("UTF8");
 
             final MessageDigest digester = MessageDigest.getInstance("MD5");
             byte[] hash = digester.digest(utf8);
 

--- a/mobile/android/tests/browser/robocop/robocop.ini
+++ b/mobile/android/tests/browser/robocop/robocop.ini
@@ -98,16 +98,17 @@ skip-if = android_version == "18"
 [src/org/mozilla/gecko/tests/testAboutHomeVisibility.java]
 [src/org/mozilla/gecko/tests/testAppMenuPathways.java]
 [src/org/mozilla/gecko/tests/testBackButtonInEditMode.java]
 [src/org/mozilla/gecko/tests/testBrowserDatabaseHelperUpgrades.java]
 [src/org/mozilla/gecko/tests/testEventDispatcher.java]
 [src/org/mozilla/gecko/tests/testGeckoRequest.java]
 [src/org/mozilla/gecko/tests/testInputConnection.java]
 [src/org/mozilla/gecko/tests/testJavascriptBridge.java]
+[src/org/mozilla/gecko/tests/testReaderCacheMigration.java]
 [src/org/mozilla/gecko/tests/testReadingListToBookmarksMigration.java]
 [src/org/mozilla/gecko/tests/testNativeCrypto.java]
 [src/org/mozilla/gecko/tests/testReaderModeTitle.java]
 [src/org/mozilla/gecko/tests/testSessionHistory.java]
 [src/org/mozilla/gecko/tests/testStateWhileLoading.java]
 [src/org/mozilla/gecko/tests/testUnifiedTelemetryClientId.java]
 
 [src/org/mozilla/gecko/tests/testAccessibleCarets.java]

new file mode 100644
--- /dev/null
+++ b/mobile/android/tests/browser/robocop/src/org/mozilla/gecko/tests/testReaderCacheMigration.java
@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.tests;
+
+import org.mozilla.gecko.GeckoProfile;
+import org.mozilla.gecko.db.BrowserDatabaseHelper;
+
+import java.io.File;
+import java.io.IOException;
+
+import static org.mozilla.gecko.tests.helpers.AssertionHelper.fAssertTrue;
+
+/**
+ * Tests that our readercache-migration works correctly.
+ *
+ * Our main concern is ensuring that the hashed path for a given url is the same in Java
+ * as it was in JS, or else our (Java-based) migration will lose track of valid cached items.
+ */
+public class testReaderCacheMigration extends JavascriptBridgeTest {
+
+    private final String[] TEST_DOMAINS = new String[] {
+            "",
+            "http://mozilla.org",
+            "https://bugzilla.mozilla.org/show_bug.cgi?id=1234315#c41",
+            "http://www.llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch.com/"
+    };
+
+    private static final String TEST_JS = "testReaderCacheMigration.js";
+
+    /**
+     * We compute the path-name in Java, and pass this through to JS, which conducts the actual
+     * equality check. Our JavascriptBridge doesn't seem to support return values, so we need
+     * to instead pass the computed path-name in at least one direction.
+     */
+    private void checkPathMatches(final String pageURL, final File cacheDir) {
+        final String hashedName = BrowserDatabaseHelper.getReaderCacheFileNameForURL(pageURL);
+
+        final File cacheFile = new File(cacheDir, hashedName);
+
+        try {
+            // We have to use the canonical path to match what the JS side will use. We could
+            // instead just match on the file name, and not the path, but this helps
+            // ensure that we've not broken any of the path finding either.
+            getJS().syncCall("check_hashed_path_matches", pageURL, cacheFile.getCanonicalPath());
+        } catch (IOException e) {
+            fAssertTrue("Unable to getCanonicalPath(), this should never happen", false);
+        }
+
+    }
+
+    public void testReaderCacheMigration() {
+        blockForReadyAndLoadJS(TEST_JS);
+
+        final File cacheDir = new File(GeckoProfile.get(getActivity()).getDir(), "readercache");
+
+        for (final String URL : TEST_DOMAINS) {
+            checkPathMatches(URL, cacheDir);
+        }
+    }
+}

new file mode 100644
--- /dev/null
+++ b/mobile/android/tests/browser/robocop/testReaderCacheMigration.js
@@ -0,0 +1,23 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+Components.utils.import("resource://gre/modules/ReaderMode.jsm");
+
+var java = new JavaBridge(this);
+
+do_register_cleanup(() => {
+  java.disconnect();
+});
+do_test_pending();
+
+function check_hashed_path_matches(url, hashedPath) {
+  var jsHashedPath = ReaderMode._toHashedPath(url);
+  do_check_eq(hashedPath, jsHashedPath);
+}
+
+function finish_test() {
+  do_test_finished();
+}
\ No newline at end of file