tests: initial integration tests

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I09ed2eea568edfaecdb800197bc36c416a6a6964

tests/integration/regression_normal_nix.nix

@@ -0,0 +1,39 @@
+# Test that normal Nix evaluation is not broken
+# This file should work identically with or without the plugin
+let
+  # Basic arithmetic
+  math = 1 + 2 * 3;
+
+  # String operations
+  str = "hello" + " " + "world";
+
+  # List operations
+  list = [1 2 3] ++ [4 5 6];
+
+  # Attrset operations
+  attrs =
+    {
+      a = 1;
+      b = 2;
+    }
+    // {c = 3;};
+
+  # Functions
+  double = x: x * 2;
+  result = double 21;
+
+  # Conditionals
+  cond =
+    if true
+    then "yes"
+    else "no";
+
+  # Let bindings
+  nested = let
+    x = 10;
+    y = 20;
+  in
+    x + y;
+in {
+  inherit math str list attrs result cond nested;
+}