diff --git a/oauthproxy_test.go b/oauthproxy_test.go
index 218b4426..b2abe379 100644
--- a/oauthproxy_test.go
+++ b/oauthproxy_test.go
@@ -657,6 +657,59 @@ func TestManualSignInStoresUserGroupsInTheSession(t *testing.T) {
 	assert.Equal(t, userGroups, s.Groups)
 }
 
+type ManualSignInValidator struct{}
+
+func (ManualSignInValidator) Validate(user, password string) bool {
+	switch {
+	case user == "admin" && password == "adminPass":
+		return true
+	default:
+		return false
+	}
+}
+
+func ManualSignInWithCredentials(t *testing.T, user, pass string) int {
+	opts := baseTestOptions()
+	err := validation.Validate(opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxy, err := NewOAuthProxy(opts, func(email string) bool {
+		return true
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxy.basicAuthValidator = ManualSignInValidator{}
+
+	rw := httptest.NewRecorder()
+	formData := url.Values{}
+	formData.Set("username", user)
+	formData.Set("password", pass)
+	signInReq, _ := http.NewRequest(http.MethodPost, "/oauth2/sign_in", strings.NewReader(formData.Encode()))
+	signInReq.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+	proxy.ServeHTTP(rw, signInReq)
+
+	return rw.Code
+}
+
+func TestManualSignInEmptyUsernameAlert(t *testing.T) {
+	statusCode := ManualSignInWithCredentials(t, "", "")
+	assert.Equal(t, http.StatusBadRequest, statusCode)
+}
+
+func TestManualSignInInvalidCredentialsAlert(t *testing.T) {
+	statusCode := ManualSignInWithCredentials(t, "admin", "")
+	assert.Equal(t, http.StatusUnauthorized, statusCode)
+}
+
+func TestManualSignInCorrectCredentials(t *testing.T) {
+	statusCode := ManualSignInWithCredentials(t, "admin", "adminPass")
+	assert.Equal(t, http.StatusFound, statusCode)
+}
+
 func TestSignInPageIncludesTargetRedirect(t *testing.T) {
 	sipTest, err := NewSignInPageTest(false)
 	if err != nil {
diff --git a/pkg/app/pagewriter/pagewriter_test.go b/pkg/app/pagewriter/pagewriter_test.go
index 2adedd19..cfea153b 100644
--- a/pkg/app/pagewriter/pagewriter_test.go
+++ b/pkg/app/pagewriter/pagewriter_test.go
@@ -57,7 +57,7 @@ var _ = Describe("Writer", func() {
 
 			It("Writes the default sign in template", func() {
 				recorder := httptest.NewRecorder()
-				writer.WriteSignInPage(recorder, request, "/redirect")
+				writer.WriteSignInPage(recorder, request, "/redirect", http.StatusOK)
 
 				body, err := ioutil.ReadAll(recorder.Result().Body)
 				Expect(err).ToNot(HaveOccurred())
@@ -104,7 +104,7 @@ var _ = Describe("Writer", func() {
 
 			It("Writes the custom sign in template", func() {
 				recorder := httptest.NewRecorder()
-				writer.WriteSignInPage(recorder, request, "/redirect")
+				writer.WriteSignInPage(recorder, request, "/redirect", http.StatusOK)
 
 				body, err := ioutil.ReadAll(recorder.Result().Body)
 				Expect(err).ToNot(HaveOccurred())
@@ -151,7 +151,7 @@ var _ = Describe("Writer", func() {
 				rw := httptest.NewRecorder()
 				req := httptest.NewRequest("", "/sign-in", nil)
 				redirectURL := "<redirectURL>"
-				in.writer.WriteSignInPage(rw, req, redirectURL)
+				in.writer.WriteSignInPage(rw, req, redirectURL, http.StatusOK)
 
 				Expect(rw.Result().StatusCode).To(Equal(in.expectedStatus))
 
@@ -166,7 +166,7 @@ var _ = Describe("Writer", func() {
 			}),
 			Entry("With an override function", writerFuncsTableInput{
 				writer: &WriterFuncs{
-					SignInPageFunc: func(rw http.ResponseWriter, req *http.Request, redirectURL string) {
+					SignInPageFunc: func(rw http.ResponseWriter, req *http.Request, redirectURL string, statusCode int) {
 						rw.WriteHeader(202)
 						rw.Write([]byte(fmt.Sprintf("%s %s", req.URL.Path, redirectURL)))
 					},
diff --git a/pkg/app/pagewriter/sign_in_page_test.go b/pkg/app/pagewriter/sign_in_page_test.go
index 804f45b0..05c0b2e9 100644
--- a/pkg/app/pagewriter/sign_in_page_test.go
+++ b/pkg/app/pagewriter/sign_in_page_test.go
@@ -54,7 +54,7 @@ var _ = Describe("SignIn Page", func() {
 		Context("WriteSignInPage", func() {
 			It("Writes the template to the response writer", func() {
 				recorder := httptest.NewRecorder()
-				signInPage.WriteSignInPage(recorder, request, "/redirect")
+				signInPage.WriteSignInPage(recorder, request, "/redirect", http.StatusOK)
 
 				body, err := ioutil.ReadAll(recorder.Result().Body)
 				Expect(err).ToNot(HaveOccurred())
@@ -68,7 +68,7 @@ var _ = Describe("SignIn Page", func() {
 				signInPage.template = tmpl
 
 				recorder := httptest.NewRecorder()
-				signInPage.WriteSignInPage(recorder, request, "/redirect")
+				signInPage.WriteSignInPage(recorder, request, "/redirect", http.StatusOK)
 
 				body, err := ioutil.ReadAll(recorder.Result().Body)
 				Expect(err).ToNot(HaveOccurred())