lsp: Fix server signature race in test

E.g. https://github.com/StyraInc/regal/actions/runs/16962142183/job/48077281888?pr=1653

Signed-off-by: Charlie Egan <charlie@styra.com>

Author: Charlie Egan

internal/lsp/server_signature_help_test.go

@@ -20,11 +20,6 @@ func TestTextDocumentSignatureHelp(t *testing.T) {
 
 	tempDir := t.TempDir()
 
-	ls := NewLanguageServer(ctx, &LanguageServerOptions{
-		LogWriter: newTestLogger(t),
-		LogLevel:  log.LevelDebug,
-	})
-
 	mainRegoURI := fileURIScheme + filepath.Join(tempDir, "main.rego")
 
 	content := `package example
@@ -33,20 +28,12 @@ allow if regex.match(` + "`foo`" + `, "bar")
 allow if count([1,2,3]) == 2
 allow if concat(",", "a", "b") == "b,a"`
 
-	ls.cache.SetFileContents(mainRegoURI, content)
-
 	builtins := map[string]*ast.Builtin{
 		"count":       ast.Count,
 		"concat":      ast.Concat,
 		"regex.match": ast.RegexMatch,
 	}
 
-	// this is needed to prepare the server for signature help queries
-	err := ls.storeBuiltinsAndCacheSignatureHelp(ctx, builtins)
-	if err != nil {
-		t.Fatalf("failed to store builtins and cache signature help: %s", err)
-	}
-
 	testCases := map[string]struct {
 		position       types.Position
 		expectedLabel  string
@@ -77,6 +64,19 @@ allow if concat(",", "a", "b") == "b,a"`
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
+			ls := NewLanguageServer(ctx, &LanguageServerOptions{
+				LogWriter: newTestLogger(t),
+				LogLevel:  log.LevelDebug,
+			})
+
+			ls.cache.SetFileContents(mainRegoURI, content)
+
+			// this is needed to prepare the server for signature help queries
+			err := ls.storeBuiltinsAndCacheSignatureHelp(ctx, builtins)
+			if err != nil {
+				t.Fatalf("failed to store builtins and cache signature help: %s", err)
+			}
+
 			params := types.SignatureHelpParams{
 				TextDocumentPositionParams: types.TextDocumentPositionParams{
 					TextDocument: types.TextDocumentIdentifier{URI: mainRegoURI},