test(ariadne): cover pipeline prerequisites

src/ariadne/BUILD

@@ -1,4 +1,4 @@
-load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library", "rust_test")
 
 rust_library(
     name = "ariadne_lib",
@@ -19,3 +19,9 @@ rust_binary(
     ],
 )
 
+rust_test(
+    name = "pipeline_test",
+    srcs = ["pipeline_test.rs"],
+    deps = [":ariadne_lib"],
+)
+

src/ariadne/pipeline_test.rs

@@ -0,0 +1,22 @@
+use ariadne::pipeline::Stage;
+
+#[test]
+fn with_prerequisites_orders_prerequisites_before_target() {
+    assert_eq!(
+        Stage::AddJumpEdges.with_prerequisites(),
+        [Stage::Parse, Stage::AddJumpEdges]
+    );
+}
+
+#[test]
+fn with_prerequisites_deduplicates_shared_prerequisites() {
+    assert_eq!(
+        Stage::All.with_prerequisites(),
+        [
+            Stage::Parse,
+            Stage::AddImplicitEdges,
+            Stage::AddInitEdges,
+            Stage::AddJumpEdges,
+        ]
+    );
+}