diff --git a/extensions/permissions/test/unit/xpcshell.toml b/extensions/permissions/test/unit/xpcshell.toml
index 5f3f3c918fac..1db677f02215 100644
--- a/extensions/permissions/test/unit/xpcshell.toml
+++ b/extensions/permissions/test/unit/xpcshell.toml
@@ -8,10 +8,7 @@ head = "head.js"
 ["test_permmanager_defaults.js"]
 
 ["test_permmanager_expiration.js"]
-skip-if = [
-  "win10_2009", # Bug 1718292
-  "win11_2009", # Bug 1797751
-]
+skip-if = ["os == 'win' && os_version == '10.2009' && processor == 'x86_64'"] # Bug 1718292
 
 ["test_permmanager_getAllByTypeSince.js"]
 
@@ -28,11 +25,10 @@ skip-if = [
 ["test_permmanager_ipc.js"]
 # This test is meant to run on a multi process mode
 # and with file urls loaded in their own child process.
-skip-if = ["!e10s"]
+run-if = ["e10s"]
 firefox-appdir = "browser"
 
 ["test_permmanager_load_invalid_entries.js"]
-skip-if = ["debug == true"]
 
 ["test_permmanager_local_files.js"]
 
@@ -41,37 +37,32 @@ skip-if = ["debug == true"]
 ["test_permmanager_matchesuri.js"]
 
 ["test_permmanager_migrate_10-11.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_11-12.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_4-7.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_4-7_no_history.js"]
-skip-if = [
-  "os == 'mac' && os_version == '11.20' && arch == 'aarch64'", # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
-  "os == 'android'"
-]
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_5-7a.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_5-7b.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_6-7a.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_6-7b.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_7-8.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_migrate_9-10.js"]
-skip-if = ["os == 'android'"] # Android doesn't use places
+run-if = ["os != 'android'"] # Android doesn't use places
 
 ["test_permmanager_notifications.js"]
 
diff --git a/extensions/pref/autoconfig/test/unit/xpcshell.toml b/extensions/pref/autoconfig/test/unit/xpcshell.toml
index 118231b4fdd2..21386ebc1a09 100644
--- a/extensions/pref/autoconfig/test/unit/xpcshell.toml
+++ b/extensions/pref/autoconfig/test/unit/xpcshell.toml
@@ -1,9 +1,5 @@
 [DEFAULT]
 head = ""
-skip-if = [
-  "os == 'android'",
-  "os == 'win' && msix", # Does not work in MSIX builds.
-]
 support-files = [
   "autoconfig-all.cfg",
   "autoconfig-latin1.cfg",
@@ -13,6 +9,8 @@ support-files = [
   "autoconfig.js",
   "autoconfig-no-sandbox.js",
 ]
+run-if = ["!msix"] # Does not work in MSIX builds.
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64' && debug"]
 
 ["test_autoconfig.js"]
 
diff --git a/extensions/spellcheck/hunspell/tests/unit/xpcshell.toml b/extensions/spellcheck/hunspell/tests/unit/xpcshell.toml
index a4f20b4797ef..0c701d2beb14 100644
--- a/extensions/spellcheck/hunspell/tests/unit/xpcshell.toml
+++ b/extensions/spellcheck/hunspell/tests/unit/xpcshell.toml
@@ -1,6 +1,5 @@
 [DEFAULT]
 head = ""
-skip-if = ["os == 'android'"]
 support-files = ["data/**"]
 firefox-appdir = "browser"
 
diff --git a/intl/benchmarks/test/xpcshell/xpcshell.toml b/intl/benchmarks/test/xpcshell/xpcshell.toml
index 5de350450266..e67b269244a1 100644
--- a/intl/benchmarks/test/xpcshell/xpcshell.toml
+++ b/intl/benchmarks/test/xpcshell/xpcshell.toml
@@ -5,13 +5,9 @@ head = "head.js"
 # to be run in CI.
 
 ["perftest_dateTimeFormat.js"]
-skip-if = ["true"]
 
 ["perftest_locale.js"]
-skip-if = ["true"]
 
 ["perftest_numberFormat.js"]
-skip-if = ["true"]
 
 ["perftest_pluralRules.js"]
-skip-if = ["true"]
diff --git a/intl/l10n/test/xpcshell.toml b/intl/l10n/test/xpcshell.toml
index e08a0eae5ff3..b93c38859f6c 100644
--- a/intl/l10n/test/xpcshell.toml
+++ b/intl/l10n/test/xpcshell.toml
@@ -16,6 +16,6 @@ head = ""
 ["test_messagecontext.js"]
 
 ["test_missing_variables.js"]
-skip-if = ["debug"] # Intentionally triggers a debug assert for missing Fluent arguments.
+run-if = ["!debug"] # Intentionally triggers a debug assert for missing Fluent arguments.
 
 ["test_pseudo.js"]
diff --git a/intl/locale/tests/unit/xpcshell.toml b/intl/locale/tests/unit/xpcshell.toml
index 5688e06e0e4c..f9d403082363 100644
--- a/intl/locale/tests/unit/xpcshell.toml
+++ b/intl/locale/tests/unit/xpcshell.toml
@@ -6,10 +6,9 @@ support-files = [
 ]
 
 ["test_bug22310.js"]
-skip-if = ["os != 'win' && os != 'mac'"]
 
 ["test_intl_on_workers.js"]
-skip-if = ["os == 'android'"] # bug 1309447
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"] # Bug 1309447
 
 ["test_langPackMatcher.js"]
 
diff --git a/ipc/testshell/tests/xpcshell.toml b/ipc/testshell/tests/xpcshell.toml
index 9e3b377e24ec..6dc063a6cd85 100644
--- a/ipc/testshell/tests/xpcshell.toml
+++ b/ipc/testshell/tests/xpcshell.toml
@@ -1,6 +1,5 @@
 [DEFAULT]
 head = ""
-skip-if = ["os == 'android'"]
 
 ["test_ipcshell.js"]
 # Bug 676963: test fails consistently on Android
diff --git a/js/xpconnect/tests/unit/xpcshell.toml b/js/xpconnect/tests/unit/xpcshell.toml
index 2299fd4a9bd5..9ea795ad7271 100644
--- a/js/xpconnect/tests/unit/xpcshell.toml
+++ b/js/xpconnect/tests/unit/xpcshell.toml
@@ -194,7 +194,7 @@ support-files = [
 ["test_defineESModuleGetters_options.js"]
 
 ["test_defineESModuleGetters_options_worker.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_envChain_frameScript.js"]
 
@@ -209,7 +209,6 @@ skip-if = ["os == 'android'"]
 ["test_exportFunction.js"]
 
 ["test_file2.js"]
-skip-if = ["os == 'android' && processor == 'x86_64'"]
 
 ["test_fileReader.js"]
 
@@ -234,21 +233,18 @@ skip-if = ["os == 'android' && processor == 'x86_64'"]
 ["test_import_global_contextual.js"]
 
 ["test_import_global_contextual_worker.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_import_global_current.js"]
 
 ["test_import_global_current_worker.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_import_global_worker.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_import_stack.js"]
-skip-if = [
-  "!nightly_build",
-  "!debug",
-]
+skip-if = ["!nightly_build"]
 
 ["test_isProxy.js"]
 
@@ -331,9 +327,7 @@ head = "head_ongc.js"
 ["test_subScriptLoader.js"]
 
 ["test_symbols_as_weak_keys.js"]
-skip-if = [
-  "!nightly_build",
-]
+skip-if = ["!nightly_build"]
 
 ["test_tearoffs.js"]
 
@@ -347,14 +341,14 @@ skip-if = [
 
 ["test_wasm_jspi_profiler.js"]
 skip-if = [
-  "tsan",
   "!nightly_build",
+  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && tsan",
 ]
 
 ["test_wasm_tailcalls_profiler.js"]
 skip-if = [
-  "tsan",
   "!nightly_build",
+  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && tsan",
 ]
 
 ["test_watchdog_default.js"]
diff --git a/memory/replace/dmd/test/xpcshell.toml b/memory/replace/dmd/test/xpcshell.toml
index ef05a8ec2607..6fc25b2af448 100644
--- a/memory/replace/dmd/test/xpcshell.toml
+++ b/memory/replace/dmd/test/xpcshell.toml
@@ -32,4 +32,3 @@ support-files = [
 
 ["test_dmd.js"]
 dmd = true
-skip-if = ["!(os=='linux' || os=='mac' || (os=='win' && !pgo))"]
diff --git a/modules/libjar/test/unit/xpcshell.toml b/modules/libjar/test/unit/xpcshell.toml
index 0670d0d95361..28050aeeb80a 100644
--- a/modules/libjar/test/unit/xpcshell.toml
+++ b/modules/libjar/test/unit/xpcshell.toml
@@ -1,6 +1,5 @@
 [DEFAULT]
 head = ""
-skip-if = ["os == 'android'"]
 support-files = [
   "data/empty",
   "data/test_bug333423.zip",
@@ -47,8 +46,7 @@ support-files = [
 ["test_bug1328865.js"]
 
 ["test_bug1550815.js"]
-# recovering from SIGBUS is temporarily disabled by bug 1583735
-skip-if = ["true"]
+run-if = ["false"] # recovering from SIGBUS is temporarily disabled by bug 1583735
 
 ["test_corrupt_1211262.js"]
 
@@ -66,11 +64,10 @@ skip-if = ["true"]
 
 ["test_fault_handler.js"]
 head = "../../zipwriter/test/unit/head_zipwriter.js"
-run-if = ["os == 'win'"] # tests windows specific exception handling
-skip-if = ["true"] # Requires elevated priviledges. See bug 1707853 and comments in test
+# run-if = ["os == 'win'"] # tests windows specific exception handling
+run-if = ["false"] # Requires elevated priviledges. See bug 1707853 and comments in test
 
 ["test_jarchannel.js"]
-skip-if = ["os == 'mac'"]
 
 ["test_jarinput_stream_zipreader_reference.js"]
 
diff --git a/modules/libmar/tests/unit/xpcshell.toml b/modules/libmar/tests/unit/xpcshell.toml
index 5ffea5544f3a..d14aa6500bbd 100644
--- a/modules/libmar/tests/unit/xpcshell.toml
+++ b/modules/libmar/tests/unit/xpcshell.toml
@@ -1,7 +1,7 @@
 [DEFAULT]
 head = "head_libmar.js"
 support-files = ["data/**"]
-skip-if = ["os == 'win' && msix"] # Updates are disabled for MSIX builds
+run-if = ["!msix"] # Updates are disabled for MSIX builds
 
 ["test_create.js"]
 
diff --git a/modules/libpref/test/unit/xpcshell.toml b/modules/libpref/test/unit/xpcshell.toml
index 03cf56d21a1b..fa4ba6dc09f9 100644
--- a/modules/libpref/test/unit/xpcshell.toml
+++ b/modules/libpref/test/unit/xpcshell.toml
@@ -26,7 +26,6 @@ support-files = [
 ["test_libPrefs.js"]
 
 ["test_locked_file_prefs.js"]
-skip-if = ["os == 'win' && socketprocess_networking"]
 support-files = [
   "data/testPrefLocked.js", "data/testPrefLockedUser.js",
 ]
@@ -39,7 +38,6 @@ head = ""
 support-files = ["data/testParser.js"]
 
 ["test_stickyprefs.js"]
-skip-if = ["os == 'win' && socketprocess_networking"]
 support-files = [
   "data/testPrefSticky.js", "data/testPrefStickyUser.js",
 ]
diff --git a/modules/libpref/test/unit_ipc/xpcshell.toml b/modules/libpref/test/unit_ipc/xpcshell.toml
index a398efa53718..7a5dc51e0163 100644
--- a/modules/libpref/test/unit_ipc/xpcshell.toml
+++ b/modules/libpref/test/unit_ipc/xpcshell.toml
@@ -1,6 +1,5 @@
 [DEFAULT]
 head = ""
-skip-if = ["os == 'android'"]
 
 ["test_existing_prefs.js"]
 
@@ -20,3 +19,4 @@ run-if = ["debug"] # Relies on debug assertions to catch failure cases.
 ["test_update_prefs.js"]
 
 ["test_user_default_prefs.js"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
diff --git a/security/manager/ssl/tests/unit/xpcshell.toml b/security/manager/ssl/tests/unit/xpcshell.toml
index be10ab52d101..4194b93017a6 100644
--- a/security/manager/ssl/tests/unit/xpcshell.toml
+++ b/security/manager/ssl/tests/unit/xpcshell.toml
@@ -5,7 +5,7 @@ firefox-appdir = "browser"
 prefs = [
   "security.pki.certificate_transparency.mode=1",
 ]
-skip-if = ["os == 'win' && msix"] # https://bugzilla.mozilla.org/show_bug.cgi?id=1809477
+run-if = ["!msix"] # Bug 1809477
 support-files = [
   "bad_certs/**",
   "ocsp_certs/**",
@@ -65,10 +65,7 @@ tags = "remote-settings blocklist psm"
 # FIPS still works on Linux, so this test doesn't make any sense there.
 # FIPS still works on Windows, but running the test to ensure that it does not
 # break with a non-ASCII profile path.
-skip-if = [
-  "os == 'android'",
-  "os == 'linux'"
-]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_certDB_export_pkcs12.js"]
 
@@ -76,13 +73,11 @@ skip-if = [
 
 ["test_certDB_import.js"]
 # nsCertificateDialogs not available in geckoview, bug 1554276
-skip-if = ["os == 'android' && processor == 'x86_64'"]
 
 ["test_certDB_import_pkcs12.js"]
 
 ["test_certDB_import_with_primary_password.js"]
 # nsCertificateDialogs not available in geckoview, bug 1554276
-skip-if = ["os == 'android' && processor == 'x86_64'"]
 
 ["test_cert_chains.js"]
 run-sequentially = "hardcoded ports"
@@ -126,7 +121,6 @@ tags = "addons psm blocklist"
 ["test_cert_version.js"]
 
 ["test_client_auth_remember_service_read.js"]
-skip-if = ["condprof"]
 
 ["test_constructX509FromBase64.js"]
 
@@ -138,24 +132,23 @@ tags = "remote-settings psm"
 ["test_crlite_preexisting.js"]
 
 ["test_ct.js"]
-# Requires hard-coded debug-only data
-skip-if = ["!debug"]
+run-if = ["debug"] # Requires hard-coded debug-only data
 run-sequentially = "hardcoded ports"
+skip-if = ["os == 'win' && os_version == '11.26100' && processor == 'x86_64' && msix"]
 
 ["test_ct_stapled.js"]
-# Requires hard-coded debug-only data
-skip-if = ["!debug"]
+run-if = ["debug"] # Requires hard-coded debug-only data
 run-sequentially = "hardcoded ports"
+skip-if = ["os == 'win' && os_version == '11.26100' && processor == 'x86_64' && msix"]
 
 ["test_data_storage.js"]
 
 ["test_db_format_pref_new.js"]
-# Android always has and always will use the new format, so
-# this test doesn't apply.
+run-if = ["os != 'android'"] # Android always has and always will use the new format, so this test doesn't apply.
 skip-if = [
-  "os == 'android'",
-  "condprof",
-]  # Bug 1769154 - as designed
+  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && opt && condprof",
+  "os == 'win' && os_version == '11.26100' && processor == 'x86_64' && opt && condprof",
+]
 
 ["test_delegated_credentials.js"]
 run-sequentially = "hardcoded ports"
@@ -171,7 +164,10 @@ run-sequentially = "hardcoded ports"
 ["test_enterprise_roots.js"]
 # This feature is implemented for Windows and OS X. However, we don't currently
 # have a way to test it on OS X.
-skip-if = ["os != 'win'"]
+run-if = [
+  "os == 'windows'",
+  "os == 'mac'",
+]
 
 ["test_ev_certs.js"]
 tags = "blocklist psm"
@@ -185,8 +181,6 @@ run-sequentially = "hardcoded ports"
 ["test_hash_algorithms.js"]
 
 ["test_hash_algorithms_wrap.js"]
-# bug 1124289 - run_test_in_child violates the sandbox on android
-skip-if = ["os == 'android'"]
 
 ["test_intermediate_basic_usage_constraints.js"]
 
@@ -200,7 +194,6 @@ tags = "blocklist psm remote-settings"
 run-sequentially = "hardcoded ports"
 
 ["test_logoutAndTeardown.js"]
-skip-if = ["socketprocess_networking && os == 'linux' && debug"]
 run-sequentially = "hardcoded ports"
 
 ["test_missing_intermediate.js"]
@@ -233,7 +226,6 @@ run-sequentially = "hardcoded ports"
 
 ["test_ocsp_private_caching.js"]
 run-sequentially = "hardcoded ports"
-skip-if = ["condprof"]  # Bug 1769154 - should look into this
 
 ["test_ocsp_required.js"]
 run-sequentially = "hardcoded ports"
@@ -248,15 +240,13 @@ run-sequentially = "hardcoded ports"
 run-sequentially = "hardcoded ports"
 
 ["test_ocsp_timeout.js"]
-skip-if = ["(os == 'win' && socketprocess_networking)"]
 run-sequentially = "hardcoded ports"
 
 ["test_ocsp_url.js"]
 run-sequentially = "hardcoded ports"
 
 ["test_oskeystore.js"]
-skip-if = ["os == 'mac' && os_version == '11.20' && arch == 'aarch64'"] # bug 1729538
-
+skip-if = ["os == 'mac' && os_version == '11.20' && arch == 'aarch64'"] # Bug 1729538
 
 ["test_osreauthenticator.js"]
 # Reauthentication has been implemented on Windows and MacOS, so running this
@@ -279,16 +269,14 @@ run-sequentially = "hardcoded ports"
 
 ["test_sdr_preexisting.js"]
 # Not relevant to Android. See the comment in the test.
-skip-if = ["os == 'android'"]
 
 ["test_sdr_preexisting_with_password.js"]
 # Not relevant to Android. See the comment in the test.
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_self_signed_certs.js"]
 
 ["test_session_resumption.js"]
-skip-if = ["os == 'win'"] # Bug 1585916
 run-sequentially = "hardcoded ports"
 
 ["test_signed_apps.js"]
@@ -297,49 +285,44 @@ run-sequentially = "hardcoded ports"
 run-sequentially = "hardcoded ports"
 
 ["test_sss_eviction.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_migration.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_originAttributes.js"]
 
 ["test_sss_readstate.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_readstate_empty.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_readstate_garbage.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_readstate_huge.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
+run-if = ["!condprof"] # Bug 1769154 - as designed
 
 ["test_sss_resetState.js"]
 
 ["test_sss_sanitizeOnShutdown.js"]
 prefs = ["privacy.sanitize.useOldClearHistoryDialog=true"]
 firefox-appdir = "browser"
-# Sanitization works differently on Android - this doesn't apply.
-# browser/modules/Sanitizer.sys.mjs used by the test isn't available in Thunderbird.
-skip-if = [
-  "os == 'android'",
-  "appname == 'thunderbird'"
+run-if = [
+  "os != 'android'", # Sanitization works differently on Android - this doesn't apply.
+  "appname == 'thunderbird'", # browser/modules/Sanitizer.sys.mjs used by the test isn't available in Thunderbird.
 ]
 
 ["test_sss_sanitizeOnShutdown_v2.js"]
 prefs = ["privacy.sanitize.useOldClearHistoryDialog=false"]
 firefox-appdir = "browser"
-# Sanitization works differently on Android - this doesn't apply.
-# browser/modules/Sanitizer.sys.mjs used by the test isn't available in Thunderbird.
-skip-if = [
-  "os == 'android'",
-  "appname == 'thunderbird'"
+run-if = [
+  "os != 'android'", # Sanitization works differently on Android - this doesn't apply.
+  "appname == 'thunderbird'", # browser/modules/Sanitizer.sys.mjs used by the test isn't available in Thunderbird.
 ]
 
 ["test_sss_savestate.js"]
-skip-if = ["condprof"]  # Bug 1769154 - as designed
 
 ["test_sts_fqdn.js"]
 
diff --git a/services/common/tests/unit/xpcshell.toml b/services/common/tests/unit/xpcshell.toml
index 35c10dfce334..c79d88b0c04c 100644
--- a/services/common/tests/unit/xpcshell.toml
+++ b/services/common/tests/unit/xpcshell.toml
@@ -10,10 +10,10 @@ support-files = ["test_storage_adapter/**"]
 ["test_async_foreach.js"]
 
 ["test_hawkclient.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_hawkrequest.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_kinto.js"]
 tags = "blocklist"
@@ -33,7 +33,7 @@ tags = "remote-settings blocklist"
 ["test_tokenauthenticatedrequest.js"]
 
 ["test_tokenserverclient.js"]
-skip-if = ["os == 'android'"]
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"]
 
 ["test_uptake_telemetry.js"]
 tags = "remote-settings"
diff --git a/services/fxaccounts/tests/xpcshell/xpcshell.toml b/services/fxaccounts/tests/xpcshell/xpcshell.toml
index cf3a35d42118..35c6b7d2f403 100644
--- a/services/fxaccounts/tests/xpcshell/xpcshell.toml
+++ b/services/fxaccounts/tests/xpcshell/xpcshell.toml
@@ -1,10 +1,7 @@
 [DEFAULT]
 head = "head.js ../../../common/tests/unit/head_helpers.js ../../../common/tests/unit/head_http.js"
 firefox-appdir = "browser"
-skip-if = [
-  "os == 'android'",
-  "appname == 'thunderbird' && !nightly_build"
-]
+skip-if = ["appname == 'thunderbird' && !nightly_build"]
 support-files = [
   "!/services/common/tests/unit/head_helpers.js",
   "!/services/common/tests/unit/head_http.js",
diff --git a/services/settings/test/unit/xpcshell.toml b/services/settings/test/unit/xpcshell.toml
index ed6b2d8461ab..d393d4d67a25 100644
--- a/services/settings/test/unit/xpcshell.toml
+++ b/services/settings/test/unit/xpcshell.toml
@@ -32,7 +32,7 @@ support-files = ["test_remote_settings_startup_bundle/**"]
 ["test_remote_settings_utils.js"]
 
 ["test_remote_settings_utils_telemetry.js"]
-skip-if = ["os == 'android'"] # bug 1739463
+skip-if = ["os == 'android' && android_version == '24' && processor == 'x86_64'"] # Bug 1739463
 
 ["test_remote_settings_worker.js"]
 
diff --git a/services/sync/tests/unit/xpcshell.toml b/services/sync/tests/unit/xpcshell.toml
index f85cdeaaba7a..381fd63458d7 100644
--- a/services/sync/tests/unit/xpcshell.toml
+++ b/services/sync/tests/unit/xpcshell.toml
@@ -26,16 +26,10 @@ support-files = [
 ["test_addon_utils.js"]
 run-sequentially = "Restarts server, can't change pref."
 tags = "addons"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_addons_engine.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
 tags = "addons"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_addons_reconciler.js"]
 skip-if = ["appname == 'thunderbird'"]
@@ -44,9 +38,6 @@ tags = "addons"
 ["test_addons_store.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
 tags = "addons"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_addons_tracker.js"]
 tags = "addons"
@@ -61,10 +52,7 @@ skip-if = ["appname == 'thunderbird'"]
 skip-if = ["appname == 'thunderbird'"]
 
 ["test_bookmark_engine.js"]
-skip-if = [
-  "appname == 'thunderbird'",
-  "tsan", # Runs unreasonably slow on TSan, bug 1612707
-]
+skip-if = ["appname == 'thunderbird'"]
 
 ["test_bookmark_order.js"]
 skip-if = ["appname == 'thunderbird'"]
@@ -79,19 +67,13 @@ skip-if = ["appname == 'thunderbird'"]
 skip-if = ["appname == 'thunderbird'"]
 
 ["test_bookmark_tracker.js"]
-skip-if = [
-  "appname == 'thunderbird'",
-  "tsan", # Runs unreasonably slow on TSan, bug 1612707
-]
+skip-if = ["appname == 'thunderbird'"]
 requesttimeoutfactor = 4
 
 ["test_bridged_engine.js"]
 
 ["test_clients_engine.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_clients_escape.js"]
 
@@ -117,15 +99,9 @@ skip-if = ["appname == 'thunderbird'"]
 
 ["test_errorhandler_1.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_errorhandler_2.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_errorhandler_filelog.js"]
 
@@ -133,17 +109,11 @@ skip-if = [
 
 ["test_extension_storage_engine.js"]
 run-sequentially = "extension-storage migration happens only once, and must be tested first."
-skip-if = [
-  "appname == 'thunderbird'",
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
+skip-if = ["appname == 'thunderbird'"]
 
 ["test_extension_storage_engine_kinto.js"]
 run-sequentially = "extension-storage migration happens only once, and must be tested first."
-skip-if = [
-  "appname == 'thunderbird'",
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
+skip-if = ["appname == 'thunderbird'"]
 
 ["test_extension_storage_tracker_kinto.js"]
 skip-if = ["appname == 'thunderbird'"]
@@ -159,9 +129,6 @@ skip-if = ["appname == 'thunderbird'"]
 
 ["test_fxa_node_reassignment.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_fxa_service_cluster.js"]
 # Finally, we test each engine.
@@ -226,10 +193,6 @@ skip-if = ["appname == 'thunderbird'"]
 
 ["test_service_attributes.js"]
 # Bug 752243: Profile cleanup frequently fails
-skip-if = [
-  "os == 'mac'",
-  "os == 'linux'",
-]
 
 ["test_service_cluster.js"]
 
@@ -248,17 +211,11 @@ skip-if = ["appname == 'thunderbird'"]
 
 ["test_service_sync_remoteSetup.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_service_sync_specified.js"]
 
 ["test_service_sync_updateEnabledEngines.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_service_verifyLogin.js"]
 
@@ -266,10 +223,6 @@ skip-if = [
 
 ["test_service_wipeServer.js"]
 # Bug 752243: Profile cleanup frequently fails
-skip-if = [
-  "os == 'mac'",
-  "os == 'linux'",
-]
 
 ["test_status.js"]
 
@@ -284,15 +237,9 @@ skip-if = [
 
 ["test_syncengine_sync.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_syncscheduler.js"]
 run-sequentially = "Frequent timeouts, bug 1395148"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 # Firefox Accounts specific tests
 
 ["test_tab_engine.js"]
@@ -308,10 +255,7 @@ skip-if = ["appname == 'thunderbird'"]
 skip-if = ["appname == 'thunderbird'"]
 
 ["test_telemetry.js"]
-skip-if = [
-  "appname == 'thunderbird'",
-  "tsan", # Unreasonably slow, bug 1612707
-]
+skip-if = ["appname == 'thunderbird'"]
 requesttimeoutfactor = 4
 
 ["test_tracker_addChanged.js"]
@@ -333,9 +277,6 @@ requesttimeoutfactor = 4
 
 ["test_utils_makeGUID.js"]
 run-sequentially = "Disproportionately slows down full test run, bug 1450316"
-skip-if = [
-  "os == 'linux' && os_version == '18.04' && processor == 'x86_64' && ccov", # Bug 1933914
-]
 
 ["test_utils_notify.js"]
 
diff --git a/storage/test/unit/xpcshell.toml b/storage/test/unit/xpcshell.toml
index 26b71fa4be34..1f86414dda9b 100644
--- a/storage/test/unit/xpcshell.toml
+++ b/storage/test/unit/xpcshell.toml
@@ -34,7 +34,7 @@ fail-if = ["os == 'android'"]
 ["test_connection_failsafe_close.js"]
 # The failsafe close mechanism asserts when performing SpinningSynchronousClose
 # on debug builds, so we can only test on non-debug builds.
-skip-if = ["debug"]
+run-if = ["!debug"]
 
 ["test_connection_interrupt.js"]
 
diff --git a/testing/xpcshell/test/unit/xpcshell.toml b/testing/xpcshell/test/unit/xpcshell.toml
index 9f9aa56d2be8..eeb7c621e2a9 100644
--- a/testing/xpcshell/test/unit/xpcshell.toml
+++ b/testing/xpcshell/test/unit/xpcshell.toml
@@ -15,11 +15,9 @@ support-files = [
 ["test_add_setup.js"]
 
 ["test_check_nsIException.js"]
-skip-if = ["os == 'win' && debug"]
 
 ["test_check_nsIException_failing.js"]
 fail-if = ["true"]
-skip-if = ["os == 'win' && debug"]
 
 ["test_do_check_matches.js"]
 
@@ -27,11 +25,9 @@ skip-if = ["os == 'win' && debug"]
 fail-if = ["true"]
 
 ["test_do_check_null.js"]
-skip-if = ["os == 'win' && debug"]
 
 ["test_do_check_null_failing.js"]
 fail-if = ["true"]
-skip-if = ["os == 'win' && debug"]
 
 ["test_do_get_tempdir.js"]
 
@@ -68,7 +64,7 @@ prefs = ["dummy.pref.from.test.file=1"]
 ["test_sample.js"]
 
 ["test_skip.js"]
-skip-if = ["true"]
+run-if = ["false"]
 
 ["test_tasks_skip.js"]