Add tests for response meta parser function

gemini.go

@@ -78,7 +78,7 @@ func GeminiParsedURL(u url.URL) (res *GeminiResponse, err error) {
 // META which is equal to "text/gemini; charset=utf-8" according to the spec.
 func ParseMeta(meta string) (string, map[string]string, error) {
 	if meta == "" {
-		return "text/gemini", make(map[string]string), nil
+		return "text/gemini", map[string]string{"charset": "utf-8"}, nil
 	}
 
 	mediatype, params, err := mime.ParseMediaType(meta)

gemini_test.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"errors"
+	"testing"
+)
+
+type ParseMetaResult struct {
+	mediatype string
+	params    map[string]string
+	err       error
+}
+
+func TestParseMeta(t *testing.T) {
+	var tests = []struct {
+		meta string
+		res  ParseMetaResult
+	}{
+		{"", ParseMetaResult{"text/gemini", map[string]string{"charset": "utf-8"}, nil}},
+		{"text/gemini;", ParseMetaResult{"text/gemini", make(map[string]string), nil}},
+		{"text/gemini; lang=en", ParseMetaResult{"text/gemini", map[string]string{"lang": "en"}, nil}},
+		{"text/gemini; charset=utf-8;", ParseMetaResult{"text/gemini", map[string]string{"charset": "utf-8"}, nil}},
+		{"text/plain; charset=utf-8;", ParseMetaResult{"text/plain", map[string]string{"charset": "utf-8"}, nil}},
+		{"text/gemini; lang=es;", ParseMetaResult{"text/gemini", map[string]string{"lang": "es"}, nil}},
+		{"text/plain; charset=utf-8;lang=ru", ParseMetaResult{"text/plain", map[string]string{"charset": "utf-8", "lang": "ru"}, nil}},
+		{"foobar", ParseMetaResult{"foobar", make(map[string]string), nil}},
+		{"foo=;", ParseMetaResult{"", make(map[string]string), errors.New("mime: expected slash after first token")}},
+		{";", ParseMetaResult{"", make(map[string]string), errors.New("mime: no media type")}},
+		{"application/octet-stream", ParseMetaResult{"application/octet-stream", make(map[string]string), nil}},
+	}
+
+	for _, test := range tests {
+		mediatype, params, err := ParseMeta(test.meta)
+		if mediatype != test.res.mediatype {
+			t.Errorf("parseMeta(%q) mediatype = %q, want %q", test.meta, mediatype, test.res.mediatype)
+		}
+		for k, v := range test.res.params {
+			if params[k] != v {
+				t.Errorf("parseMeta(%q) params[%q] = %q, want %q", test.meta, k, params[k], v)
+			}
+		}
+		if err == nil && test.res.err == nil {
+			continue
+		}
+		if (err != nil && test.res.err == nil) || (err.Error() != test.res.err.Error()) {
+			t.Errorf("parseMeta(%q) err = %q, want %q", test.meta, err, test.res.err)
+		}
+	}
+}