test: copy over most tests, add new tests for soonix

tests/helpers_test.nix

@@ -0,0 +1,68 @@
+{
+  pkgs,
+  cilib,
+  ...
+}: {
+  suites."Helpers" = {
+    pos = __curPos;
+    tests = let
+      inherit (cilib) helpers;
+    in [
+      {
+        name = "appendToAfterScript";
+        expected = {
+          after_script = ["echo after_script" "finalize_nix_ci"];
+        };
+        actual = helpers.appendToAfterScript ["finalize_nix_ci"] {
+          after_script = ["echo after_script"];
+        };
+      }
+      {
+        name = "prependToBeforeScript";
+        expected = {
+          before_script = ["setup_nix_ci" "echo before_script"];
+        };
+        actual = helpers.prependToBeforeScript ["setup_nix_ci"] {
+          before_script = ["echo before_script"];
+        };
+      }
+      {
+        name = "toYaml";
+        expected = ''{"hello":"world"}'';
+        actual = builtins.readFile (helpers.toYaml "test" {hello = "world";});
+      }
+      {
+        name = "filterAttrsRec";
+        expected = {world = "world";};
+        actual = helpers.filterAttrsRec (_n: v: v != null) {
+          hello = null;
+          world = "world";
+        };
+      }
+      {
+        name = "filterJobVariables with store paths";
+        expected = {
+          HELLO = "${pkgs.hello}";
+          MULTIPLE = "${pkgs.hello}:${pkgs.hello}";
+        };
+        actual = helpers.filterJobVariables true {
+          variables = {
+            HELLO = "${pkgs.hello}";
+            WORLD = "world";
+            MULTIPLE = "${pkgs.hello}:${pkgs.hello}";
+          };
+        };
+      }
+      {
+        name = "filterJobVariables without store paths";
+        expected = {WORLD = "world";};
+        actual = helpers.filterJobVariables false {
+          variables = {
+            HELLO = "${pkgs.hello}";
+            WORLD = "world";
+          };
+        };
+      }
+    ];
+  };
+}