diff --git a/mastodon_test.go b/mastodon_test.go
new file mode 100644
index 0000000..d0ad68d
--- /dev/null
+++ b/mastodon_test.go
@@ -0,0 +1,77 @@
+package mastodon
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestAuthenticate(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.FormValue("username") != "valid" || r.FormValue("password") != "user" {
+			http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+			return
+		}
+		fmt.Fprintln(w, `{"AccessToken": "zoo"}`)
+		return
+	}))
+	defer ts.Close()
+
+	client := NewClient(&Config{
+		Server:       ts.URL,
+		ClientID:     "foo",
+		ClientSecret: "bar",
+	})
+	err := client.Authenticate("invalid", "user")
+	if err == nil {
+		t.Fatalf("should be fail: %v", err)
+	}
+
+	client = NewClient(&Config{
+		Server:       ts.URL,
+		ClientID:     "foo",
+		ClientSecret: "bar",
+	})
+	err = client.Authenticate("valid", "user")
+	if err != nil {
+		t.Fatalf("should not be fail: %v", err)
+	}
+}
+
+func TestPostStatus(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Authorization") != "Bearer zoo" {
+			http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+			return
+		}
+		fmt.Fprintln(w, `{"AccessToken": "zoo"}`)
+		return
+	}))
+	defer ts.Close()
+
+	client := NewClient(&Config{
+		Server:       ts.URL,
+		ClientID:     "foo",
+		ClientSecret: "bar",
+	})
+	_, err := client.PostStatus(&Toot{
+		Status: "foobar",
+	})
+	if err == nil {
+		t.Fatalf("should be fail: %v", err)
+	}
+
+	client = NewClient(&Config{
+		Server:       ts.URL,
+		ClientID:     "foo",
+		ClientSecret: "bar",
+		AccessToken:  "zoo",
+	})
+	_, err = client.PostStatus(&Toot{
+		Status: "foobar",
+	})
+	if err != nil {
+		t.Fatalf("should not be fail: %v", err)
+	}
+}