tests/delta: add tests

Create a new set of tests to verify the new module's behavior.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

tests/modules/programs/delta/delta-basic.nix

@@ -0,0 +1,35 @@
+{ config, ... }:
+
+{
+  programs.delta = {
+    enable = true;
+    package = config.lib.test.mkStubPackage {
+      name = "delta";
+      buildScript = ''
+        mkdir -p $out/bin
+        touch $out/bin/delta
+        chmod 755 $out/bin/delta
+      '';
+    };
+    options = {
+      features = "line-numbers decorations";
+      syntax-theme = "Dracula";
+      decorations = {
+        commit-decoration-style = "bold yellow box ul";
+        file-style = "bold yellow ul";
+        file-decoration-style = "none";
+      };
+    };
+  };
+  programs.git.enable = true;
+
+  nmt.script = ''
+    # Git config should NOT contain delta configuration since enableGitIntegration is false by default
+    assertFileNotRegex home-files/.config/git/config 'pager = .*/bin/delta'
+    assertFileNotRegex home-files/.config/git/config 'diffFilter = .*/bin/delta'
+
+    # Verify the wrapper passes the config flag
+    # The wrapper script should contain --config flag
+    assertFileRegex home-path/bin/delta '\-\-config'
+  '';
+}