diff --git a/browser/base/content/test/tabs/browser.ini b/browser/base/content/test/tabs/browser.ini
index d57c6ee0b49c..4b3253e3e24a 100644
--- a/browser/base/content/test/tabs/browser.ini
+++ b/browser/base/content/test/tabs/browser.ini
@@ -26,7 +26,6 @@ support-files =
   file_about_child.html
   file_about_parent.html
 [browser_e10s_switchbrowser.js]
-fail-if = fission
 [browser_e10s_about_process.js]
 [browser_e10s_mozillaweb_process.js]
 [browser_e10s_chrome_process.js]
diff --git a/browser/base/content/test/trackingUI/browser.ini b/browser/base/content/test/trackingUI/browser.ini
index 0d0bc30479bc..8af230a381fe 100644
--- a/browser/base/content/test/trackingUI/browser.ini
+++ b/browser/base/content/test/trackingUI/browser.ini
@@ -13,15 +13,20 @@ support-files =
 
 [browser_trackingUI_3.js]
 [browser_trackingUI_animation.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_animation_2.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_appMenu.js]
 [browser_trackingUI_background_tabs.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_categories.js]
 skip-if = fission && debug # Causing crashes [@ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)]
 [browser_trackingUI_cookies_subview.js]
 skip-if = fission
 [browser_trackingUI_cryptominers.js]
-skip-if = fission && debug # Causing crashes [@ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)]
+skip-if =
+  fission && debug || # Causing crashes [@ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)]
+  fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_fetch.js]
 skip-if = fission && debug # Causing crashes [@ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)]
 support-files =
@@ -29,20 +34,30 @@ support-files =
   file_trackingUI_fetch.js
   file_trackingUI_fetch.js^headers^
 [browser_trackingUI_fingerprinters.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_open_preferences.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_pbmode_exceptions.js]
 skip-if = fission # Crashes: @ mozilla::dom::BrowserBridgeParent::RecvShow(mozilla::gfx::IntSizeTyped<mozilla::ScreenPixel> const&, bool const&, nsSizeMode const&)
 [browser_trackingUI_report_breakage.js]
 skip-if = fission || debug || asan # Bug 1546797
 [browser_trackingUI_socialtracking.js]
-skip-if = fission && debug # Crashes: @ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)
+skip-if =
+  fission && debug || # Crashes: @ mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*, nsISupports*)
+  fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_shield_visibility.js]
 skip-if = fission && debug #Bug 1574939
 [browser_trackingUI_state.js]
 skip-if = serviceworker_e10s || (fission && debug) # see https://bugzilla.mozilla.org/show_bug.cgi?id=1511303#c1 #Bug 1574939
 [browser_trackingUI_state_reset.js]
-skip-if = fission && debug #Bug 1574939
+skip-if =
+  fission && debug || #Bug 1574939
+  fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_telemetry.js]
-skip-if = fission && debug #Bug 1574939
+skip-if =
+  fission && debug || #Bug 1574939
+  fission # Times out under Fission with DocumentChannel enabled.
 [browser_trackingUI_trackers_subview.js]
-skip-if = fission && debug #Bug 1574939
+skip-if =
+  fission && debug || #Bug 1574939
+  fission # Times out under Fission with DocumentChannel enabled.
diff --git a/browser/components/extensions/test/browser/browser.ini b/browser/components/extensions/test/browser/browser.ini
index 4a433f240b3d..91d58795a23e 100644
--- a/browser/components/extensions/test/browser/browser.ini
+++ b/browser/components/extensions/test/browser/browser.ini
@@ -220,7 +220,6 @@ skip-if = os == "linux" && debug && bits == 32 # Bug 1350189
 [browser_ext_tabs_discard.js]
 skip-if = !e10s
 [browser_ext_tabs_discarded.js]
-fail-if = fission
 [browser_ext_tabs_duplicate.js]
 [browser_ext_tabs_events.js]
 skip-if = true # Bug 1521363
diff --git a/browser/components/safebrowsing/content/test/browser.ini b/browser/components/safebrowsing/content/test/browser.ini
index 5704dd909a47..6f0e08145760 100644
--- a/browser/components/safebrowsing/content/test/browser.ini
+++ b/browser/components/safebrowsing/content/test/browser.ini
@@ -9,3 +9,4 @@ support-files =
 skip-if = os == "mac" || e10s # e10s: Bug 1248632
 [browser_whitelisted.js]
 [browser_mixedcontent_aboutblocked.js]
+skip-if = fission # Times out under Fission with DocumentChannel enabled.
diff --git a/dom/tests/mochitest/ajax/offline/browser.ini b/dom/tests/mochitest/ajax/offline/browser.ini
index 3935dd31521c..f2b1b4dc7e18 100644
--- a/dom/tests/mochitest/ajax/offline/browser.ini
+++ b/dom/tests/mochitest/ajax/offline/browser.ini
@@ -5,4 +5,5 @@ support-files =
   file_simpleManifest.cacheManifest
 
 [browser_disableAppcache.js]
+fail-if = fission
 skip-if = !e10s || (toolkit == 'android') || debug # Slow
diff --git a/taskcluster/taskgraph/transforms/tests.py b/taskcluster/taskgraph/transforms/tests.py
index ad017a5ee611..ef90f1102bbc 100644
--- a/taskcluster/taskgraph/transforms/tests.py
+++ b/taskcluster/taskgraph/transforms/tests.py
@@ -160,7 +160,8 @@ TEST_VARIANTS = {
             'tier': 2,
             'mozharness': {
                 'extra-options': ['--setpref="fission.autostart=true"',
-                                  '--setpref="dom.serviceWorkers.parent_intercept=true"'],
+                                  '--setpref="dom.serviceWorkers.parent_intercept=true"',
+                                  '--setpref="browser.tabs.documentchannel=true"'],
             },
         },
     },
diff --git a/testing/mochitest/mochitest_options.py b/testing/mochitest/mochitest_options.py
index c8f644df90cc..c45245311054 100644
--- a/testing/mochitest/mochitest_options.py
+++ b/testing/mochitest/mochitest_options.py
@@ -833,6 +833,7 @@ class MochitestArguments(ArgumentContainer):
         if options.enable_fission:
             options.extraPrefs.append("fission.autostart=true")
             options.extraPrefs.append("dom.serviceWorkers.parent_intercept=true")
+            options.extraPrefs.append("browser.tabs.documentchannel=true")
 
         options.leakThresholds = {
             "default": options.defaultLeakThreshold,
diff --git a/toolkit/components/antitracking/test/browser/browser.ini b/toolkit/components/antitracking/test/browser/browser.ini
index 11e13b3961cf..f528fbfee5a4 100644
--- a/toolkit/components/antitracking/test/browser/browser.ini
+++ b/toolkit/components/antitracking/test/browser/browser.ini
@@ -68,6 +68,7 @@ skip-if = fission || (os == "linux" && asan)
 [browser_blockingNoOpener.js]
 skip-if = fission || (os == "linux" && asan)
 [browser_doublyNestedTracker.js]
+fail-if = fission # Fails under Fission with DocumentChannel enabled.
 [browser_existingCookiesForSubresources.js]
 [browser_firstPartyCookieRejectionHonoursAllowList.js]
 [browser_imageCache4.js]
diff --git a/toolkit/components/passwordmgr/test/mochitest/mochitest.ini b/toolkit/components/passwordmgr/test/mochitest/mochitest.ini
index 3edfe99e457c..069e5a6bcfa7 100644
--- a/toolkit/components/passwordmgr/test/mochitest/mochitest.ini
+++ b/toolkit/components/passwordmgr/test/mochitest/mochitest.ini
@@ -163,6 +163,5 @@ skip-if =
   fission # Intermittently times out under Fission.
 [test_xhr_2.html]
 [test_xml_load.html]
-fail-if = fission
 skip-if = toolkit == 'android' # Tests desktop prompts