diff --git a/src/zen/spaces/ZenSpaceManager.mjs b/src/zen/spaces/ZenSpaceManager.mjs
index d5c118b11..d1f6a609d 100644
--- a/src/zen/spaces/ZenSpaceManager.mjs
+++ b/src/zen/spaces/ZenSpaceManager.mjs
@@ -1551,7 +1551,7 @@ class nsZenWorkspaces {
         !tab.hasAttribute("pending")
     );
 
-    await gBrowser.explicitUnloadTabs(tabsToUnload); // TODO: unit test this
+    await gBrowser.explicitUnloadTabs(tabsToUnload);
   }
 
   moveTabToWorkspace(tab, workspaceID) {
diff --git a/src/zen/tests/spaces/browser.toml b/src/zen/tests/spaces/browser.toml
index ac77baa44..deacec1f7 100644
--- a/src/zen/tests/spaces/browser.toml
+++ b/src/zen/tests/spaces/browser.toml
@@ -24,4 +24,6 @@ support-files = [
 
 ["browser_private_mode_startup.js"]
 
+["browser_unload_all_other_spaces.js"]
+
 ["browser_workspace_bookmarks.js"]
diff --git a/src/zen/tests/spaces/browser_unload_all_other_spaces.js b/src/zen/tests/spaces/browser_unload_all_other_spaces.js
new file mode 100644
index 000000000..0280519c1
--- /dev/null
+++ b/src/zen/tests/spaces/browser_unload_all_other_spaces.js
@@ -0,0 +1,162 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_setup(async function () {});
+
+// verify that with only one workspace, regular tabs should remain loaded
+add_task(async function test_UnloadAllOtherWorkspace_oneWorkspace() {
+  const workspace =
+    await gZenWorkspaces.createAndSaveWorkspace("Test Workspace");
+  const workspaceId = workspace.uuid;
+  await gZenWorkspaces.changeWorkspace(workspace);
+
+  const tabs = [];
+  for (let i = 0; i < 3; i++) {
+    const tab = await BrowserTestUtils.openNewForegroundTab(
+      window.gBrowser,
+      `data:text/html,<title>Hi! I am regular tab ${i}</title>`,
+      true,
+      { skipAnimation: true }
+    );
+    tabs.push(tab);
+  }
+
+  for (const tab of tabs) {
+    ok(!tab.hasAttribute("pending"), "Tab should not be pending before unload");
+    ok(tab.linkedPanel, "Tab should have linked panel before unload");
+  }
+
+  await gZenWorkspaces.unloadAllOtherWorkspaces();
+
+  for (const tab of tabs) {
+    ok(!tab.hasAttribute("pending"), "Tab should not be pending after unload");
+    ok(tab.linkedPanel, "Tab should have linked panel after unload");
+  }
+
+  await gZenWorkspaces.removeWorkspace(workspaceId);
+});
+
+// with multiple workspaces, only regular tabs in other workspaces should be unloaded
+add_task(async function test_UnloadAllOtherWorkspace_multipleWorkspaces() {
+  const inactiveWorkspace =
+    await gZenWorkspaces.createAndSaveWorkspace("Inactive Workspace");
+  const activeWorkspace =
+    await gZenWorkspaces.createAndSaveWorkspace("Active Workspace");
+
+  const inactiveWorkspaceId = inactiveWorkspace.uuid;
+  const activeWorkspaceId = activeWorkspace.uuid;
+
+  const inactiveWorkspaceTabs = [];
+  for (let i = 0; i < 2; i++) {
+    const tab = await BrowserTestUtils.openNewForegroundTab(
+      gBrowser,
+      `data:text/html,<title>Regular Tab ${i} in Inactive</title>`,
+      true,
+      { skipAnimation: true }
+    );
+    tab.setAttribute("zen-workspace-id", inactiveWorkspaceId);
+    inactiveWorkspaceTabs.push(tab);
+  }
+
+  const activeWorkspaceTabs = [];
+  for (let i = 0; i < 2; i++) {
+    const tab = await BrowserTestUtils.openNewForegroundTab(
+      gBrowser,
+      `data:text/html,<title>Regular Tab ${i} in Active</title>`,
+      true,
+      { skipAnimation: true }
+    );
+    tab.setAttribute("zen-workspace-id", activeWorkspaceId);
+    activeWorkspaceTabs.push(tab);
+  }
+
+  await gZenWorkspaces.unloadAllOtherWorkspaces();
+
+  for (const tab of activeWorkspaceTabs) {
+    ok(
+      !tab.hasAttribute("pending"),
+      "Tab in active workspace should not be unloaded"
+    );
+    ok(tab.linkedPanel, "Tab in active workspace should have linked panel");
+  }
+
+  for (const tab of inactiveWorkspaceTabs) {
+    ok(
+      tab.hasAttribute("pending"),
+      "Tab in inactive workspace should be unloaded"
+    );
+    ok(
+      !tab.linkedPanel,
+      "Tab in inactive workspace should not have linked panel"
+    );
+  }
+  await gZenWorkspaces.removeWorkspace(inactiveWorkspaceId);
+  await gZenWorkspaces.removeWorkspace(activeWorkspaceId);
+});
+
+// essentials in any workspace are not unloaded
+add_task(async function test_UnloadAllOtherWorkspace_essentials() {
+  const activeWorkspace =
+    await gZenWorkspaces.createAndSaveWorkspace("Active Workspace");
+  const inactiveWorkspace =
+    await gZenWorkspaces.createAndSaveWorkspace("Inactive Workspace");
+
+  const activeWorkspaceId = activeWorkspace.uuid;
+  const inactiveWorkspaceId = inactiveWorkspace.uuid;
+
+  const activeWorkspaceTabs = [];
+  for (let i = 0; i < 2; i++) {
+    const tab = await BrowserTestUtils.openNewForegroundTab(
+      gBrowser,
+      `data:text/html,<title>Essential Tab ${i} in Active</title>`,
+      true,
+      { skipAnimation: true }
+    );
+    tab.setAttribute("zen-workspace-id", activeWorkspaceId);
+    tab.setAttribute("zen-essential", "true");
+    activeWorkspaceTabs.push(tab);
+  }
+
+  const inactiveWorkspaceTabs = [];
+  for (let i = 0; i < 2; i++) {
+    const tab = await BrowserTestUtils.openNewForegroundTab(
+      gBrowser,
+      `data:text/html,<title>Essential Tab ${i} in Inactive</title>`,
+      true,
+      { skipAnimation: true }
+    );
+    gZenPinnedTabManager.addToEssentials(tab);
+    inactiveWorkspaceTabs.push(tab);
+  }
+
+  await gZenWorkspaces.unloadAllOtherWorkspaces();
+
+  for (const tab of activeWorkspaceTabs) {
+    ok(
+      !tab.hasAttribute("pending"),
+      "Essential Tab in active workspace should not be unloaded"
+    );
+    ok(
+      tab.linkedPanel,
+      "Essential Tab in active workspace should have linked panel"
+    );
+  }
+
+  for (const tab of inactiveWorkspaceTabs) {
+    ok(
+      !tab.hasAttribute("pending"),
+      "Essential Tab in inactive workspace should not be unloaded"
+    );
+    ok(
+      tab.linkedPanel,
+      "Essential Tab in inactive workspace should have linked panel"
+    );
+  }
+  for (const tab of inactiveWorkspaceTabs) {
+    gBrowser.removeTab(tab);
+  }
+  await gZenWorkspaces.removeWorkspace(inactiveWorkspaceId);
+  await gZenWorkspaces.removeWorkspace(activeWorkspaceId);
+});