diff --git a/tests/asserts.nix b/tests/asserts.nix
new file mode 100644
index 00000000..e6813b28
--- /dev/null
+++ b/tests/asserts.nix
@@ -0,0 +1,43 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  options.test.asserts = {
+    warnings = {
+      enable = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Whether warning asserts are enabled.";
+      };
+
+      expected = mkOption {
+        type = types.listOf types.str;
+        default = [ ];
+        description = ''
+          List of expected warnings.
+        '';
+      };
+    };
+  };
+
+  config = mkIf config.test.asserts.warnings.enable {
+    home.file = {
+      "asserts/warnings.actual".text = concatStringsSep ''
+
+        --
+      '' config.warnings;
+    };
+
+    nmt.script = ''
+      assertFileContent \
+        home-files/asserts/warnings.actual \
+        ${
+          pkgs.writeText "warnings.expected" (concatStringsSep ''
+
+            --
+          '' config.test.asserts.warnings.expected)
+        }
+    '';
+  };
+}
diff --git a/tests/default.nix b/tests/default.nix
index 3905f654..33a22e2b 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -25,6 +25,8 @@ let
       # Avoid including documentation since this will cause
       # unnecessary rebuilds of the tests.
       manual.manpages.enable = false;
+
+      imports = [ ./asserts.nix ];
     }
   ];
 
diff --git a/tests/modules/programs/git/git-with-str-extra-config.nix b/tests/modules/programs/git/git-with-str-extra-config.nix
index 3dbc497a..b2294c65 100644
--- a/tests/modules/programs/git/git-with-str-extra-config.nix
+++ b/tests/modules/programs/git/git-with-str-extra-config.nix
@@ -14,6 +14,12 @@ with lib;
       userName = "John Doe";
     };
 
+    test.asserts.warnings.expected = [''
+      Using programs.git.extraConfig as a string option is
+      deprecated and will be removed in the future. Please
+      change to using it as an attribute set instead.
+    ''];
+
     nmt.script = ''
       assertFileExists home-files/.config/git/config
       assertFileContent home-files/.config/git/config \
diff --git a/tests/modules/programs/lieer/lieer.nix b/tests/modules/programs/lieer/lieer.nix
index 2ce4fb4e..e0ade636 100644
--- a/tests/modules/programs/lieer/lieer.nix
+++ b/tests/modules/programs/lieer/lieer.nix
@@ -8,7 +8,10 @@ with lib;
   config = {
     programs.lieer.enable = true;
 
-    accounts.email.accounts = { "hm@example.com".lieer.enable = true; };
+    accounts.email.accounts."hm@example.com" = {
+      lieer.enable = true;
+      notmuch.enable = true;
+    };
 
     nixpkgs.overlays = [
       (self: super: { gmailieer = pkgs.writeScriptBin "dummy-gmailieer" ""; })
diff --git a/tests/modules/programs/waybar/broken-settings.nix b/tests/modules/programs/waybar/broken-settings.nix
index f5ac3946..d0e13150 100644
--- a/tests/modules/programs/waybar/broken-settings.nix
+++ b/tests/modules/programs/waybar/broken-settings.nix
@@ -66,6 +66,10 @@ in {
       }];
     };
 
+    # Remove when https://github.com/nix-community/home-manager/issues/1686 is
+    # fixed.
+    test.asserts.warnings.enable = false;
+
     nmt.description = ''
       Test for the broken configuration
       https://github.com/nix-community/home-manager/pull/1329#issuecomment-653253069
diff --git a/tests/modules/programs/waybar/settings-complex.nix b/tests/modules/programs/waybar/settings-complex.nix
index 1756ae12..16ceccb6 100644
--- a/tests/modules/programs/waybar/settings-complex.nix
+++ b/tests/modules/programs/waybar/settings-complex.nix
@@ -50,6 +50,10 @@ in {
       }];
     };
 
+    # Remove when https://github.com/nix-community/home-manager/issues/1686 is
+    # fixed.
+    test.asserts.warnings.enable = false;
+
     nmt.script = ''
       assertPathNotExists home-files/.config/waybar/style.css
       assertFileContent \
diff --git a/tests/modules/services/lieer/lieer-service.nix b/tests/modules/services/lieer/lieer-service.nix
index 03dcdc74..60e00e0c 100644
--- a/tests/modules/services/lieer/lieer-service.nix
+++ b/tests/modules/services/lieer/lieer-service.nix
@@ -11,6 +11,7 @@ with lib;
     accounts.email.accounts = {
       "hm@example.com".lieer.enable = true;
       "hm@example.com".lieer.sync.enable = true;
+      "hm@example.com".notmuch.enable = true;
     };
 
     nixpkgs.overlays = [