Add tests to check for bad URL bases

tests/data.rs

@@ -29,6 +29,7 @@ fn check_invariants(url: &Url) {
 fn run_parsing(input: &str, base: &str, expected: Result<ExpectedAttributes, ()>) {
     let base = match Url::parse(&base) {
         Ok(base) => base,
+        Err(_) if expected.is_err() => return,
         Err(message) => panic!("Error parsing base {:?}: {}", base, message)
     };
     let (url, expected) = match (base.join(&input), expected) {

tests/urltestdata.json

@@ -4461,5 +4461,87 @@
     "search": "",
     "searchParams": "",
     "hash": ""
+  },
+  "Bad bases",
+  {
+    "input": "test-a.html",
+    "base": "a",
+    "failure": true
+  },
+  {
+    "input": "test-a-slash.html",
+    "base": "a/",
+    "failure": true
+  },
+  {
+    "input": "test-a-slash-slash.html",
+    "base": "a//",
+    "failure": true
+  },
+  {
+    "input": "test-a-colon.html",
+    "base": "a:",
+    "failure": true
+  },
+  {
+    "input": "test-a-colon-slash.html",
+    "base": "a:/",
+    "href": "a:/test-a-colon-slash.html",
+    "protocol": "a:",
+    "username": "",
+    "password": "",
+    "host": "",
+    "hostname": "",
+    "port": "",
+    "pathname": "/test-a-colon-slash.html",
+    "search": "",
+    "hash": ""
+  },
+  {
+    "input": "test-a-colon-slash-slash.html",
+    "base": "a://",
+    "href": "a:///test-a-colon-slash-slash.html",
+    "protocol": "a:",
+    "username": "",
+    "password": "",
+    "host": "",
+    "hostname": "",
+    "port": "",
+    "pathname": "/test-a-colon-slash-slash.html",
+    "search": "",
+    "hash": ""
+  },
+  {
+    "input": "test-a-colon-b.html",
+    "base": "a:b",
+    "failure": true
+  },
+  {
+    "input": "test-a-colon-slash-b.html",
+    "base": "a:/b",
+    "href": "a:/test-a-colon-slash-b.html",
+    "protocol": "a:",
+    "username": "",
+    "password": "",
+    "host": "",
+    "hostname": "",
+    "port": "",
+    "pathname": "/test-a-colon-slash-b.html",
+    "search": "",
+    "hash": ""
+  },
+  {
+    "input": "test-a-colon-slash-slash-b.html",
+    "base": "a://b",
+    "href": "a://b/test-a-colon-slash-slash-b.html",
+    "protocol": "a:",
+    "username": "",
+    "password": "",
+    "host": "b",
+    "hostname": "b",
+    "port": "",
+    "pathname": "/test-a-colon-slash-slash-b.html",
+    "search": "",
+    "hash": ""
   }
 ]