test: http2 test coverage for assertValidPseudoHeader

PR-URL: nodejs#15105
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

test/parallel/test-http2-util-assert-valid-pseudoheader.js

@@ -0,0 +1,31 @@
+// Flags: --expose-internals
+'use strict';
+
+const common = require('../common');
+
+// Tests the assertValidPseudoHeader function that is used within the
+// mapToHeaders function. The assert function is not exported so we
+// have to test it through mapToHeaders
+
+const { mapToHeaders } = require('internal/http2/util');
+const assert = require('assert');
+
+function isNotError(val) {
+  assert(!(val instanceof Error));
+}
+
+function isError(val) {
+  common.expectsError({
+    code: 'ERR_HTTP2_INVALID_PSEUDOHEADER',
+    type: Error,
+    message: '":foo" is an invalid pseudoheader or is used incorrectly'
+  })(val);
+}
+
+isNotError(mapToHeaders({ ':status': 'a' }));
+isNotError(mapToHeaders({ ':path': 'a' }));
+isNotError(mapToHeaders({ ':authority': 'a' }));
+isNotError(mapToHeaders({ ':scheme': 'a' }));
+isNotError(mapToHeaders({ ':method': 'a' }));
+
+isError(mapToHeaders({ ':foo': 'a' }));