--- a/devtools/client/framework/test/browser.ini
+++ b/devtools/client/framework/test/browser.ini
@@ -114,16 +114,17 @@ skip-if = e10s # Bug 1069044 - destroyIn
 [browser_toolbox_telemetry_enter.js]
 [browser_toolbox_telemetry_exit.js]
 [browser_toolbox_textbox_context_menu.js]
 [browser_toolbox_theme.js]
 [browser_toolbox_theme_registration.js]
 [browser_toolbox_toggle.js]
 [browser_toolbox_tool_ready.js]
 [browser_toolbox_tool_remote_reopen.js]
+[browser_toolbox_toolbar_minimum_width.js]
 [browser_toolbox_toolbar_overflow.js]
 [browser_toolbox_toolbar_overflow_button_visibility.js]
 [browser_toolbox_toolbar_reorder_by_dnd.js]
 [browser_toolbox_toolbar_reorder_by_width.js]
 [browser_toolbox_toolbar_reorder_with_extension.js]
 [browser_toolbox_tools_per_toolbox_registration.js]
 [browser_toolbox_view_source_01.js]
 [browser_toolbox_view_source_02.js]

new file mode 100644
--- /dev/null
+++ b/devtools/client/framework/test/browser_toolbox_toolbar_minimum_width.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test that all of buttons of tool tab go to the overflowed menu when the devtool's
+// width is narrow.
+
+const SIDEBAR_WIDTH_PREF = "devtools.toolbox.sidebar.width";
+
+const { Toolbox } = require("devtools/client/framework/toolbox");
+
+add_task(async function(pickerEnable, commandsEnable) {
+  // 74px is Chevron(26px) + Meatball(24px) + Close(24px)
+  // devtools-browser.css defined this minimum width by using min-width.
+  Services.prefs.setIntPref(SIDEBAR_WIDTH_PREF, 74);
+  registerCleanupFunction(function() {
+    Services.prefs.clearUserPref(SIDEBAR_WIDTH_PREF);
+  });
+  const tab = await addTab("about:blank");
+
+  info("Open devtools on the Inspector in a side dock");
+  const toolbox = await openToolboxForTab(tab, "inspector", Toolbox.HostType.SIDE);
+  await waitUntil(() => toolbox.doc.querySelector(".tools-chevron-menu"));
+
+  const menuPopup = await openChevronMenu(toolbox);
+
+  // Check that all of tools is overflowed.
+  toolbox.panelDefinitions.forEach(({id}) => {
+    const menuItem = toolbox.doc.getElementById("tools-chevron-menupopup-" + id);
+    const tab = toolbox.doc.getElementById("toolbox-tab-" + id);
+    ok(menuItem, id + " is in the overflowed menu");
+    ok(!tab, id + " tab does not exist");
+  });
+
+  info("Closing the chevron popup menu");
+  const onPopupHidden = once(menuPopup, "popuphidden");
+  menuPopup.hidePopup();
+  await onPopupHidden;
+});