chore: Add tests

compiler/test/graindoc/singleReturn.input.gr

@@ -0,0 +1,7 @@
+module SingleReturn
+
+/**
+ * @returns first return
+ * @returns second return
+ */
+provide let test = () => 1

compiler/test/graindoc/singleSince.input.gr

@@ -0,0 +1,7 @@
+module SingleSince
+
+/**
+ * @since v1.0.0
+ * @since v1.0.0
+ */
+provide let test = () => print("t")

compiler/test/runner.re

@@ -487,3 +487,14 @@ let makeGrainDocRunner = (test, name, filename, arguments) => {
     },
   );
 };
+
+let makeGrainDocErrorRunner = (test, name, filename, expected, arguments) => {
+  test(
+    name,
+    ({expect}) => {
+      let infile = gaindoc_in_file(filename);
+      let (result, _) = doc(infile, arguments);
+      expect.string(result).toMatch(expected);
+    },
+  );
+};

compiler/test/suites/graindoc.re

@@ -9,6 +9,7 @@ describe("graindoc", ({test, testSkip}) => {
     Sys.backend_type == Other("js_of_ocaml") ? testSkip : test;
 
   let assertGrianDocOutput = makeGrainDocRunner(test_or_skip);
+  let assertGrainDocError = makeGrainDocErrorRunner(test_or_skip);
   ();
   assertGrianDocOutput("noDoc", "noDoc", [||]);
   assertGrianDocOutput(
@@ -18,4 +19,16 @@ describe("graindoc", ({test, testSkip}) => {
   );
   assertGrianDocOutput("since", "since", [|"--current-version=v0.2.0"|]);
   assertGrianDocOutput("example", "example", [|"--current-version=v0.2.0"|]);
+  assertGrainDocError(
+    "singleSince",
+    "singleSince",
+    "Attribute @since is only allowed to appear once.",
+    [|"--current-version=v0.2.0"|],
+  );
+  assertGrainDocError(
+    "singleReturn",
+    "singleReturn",
+    "Attribute @returns is only allowed to appear once.",
+    [|"--current-version=v0.2.0"|],
+  );
 });