diff --git a/middleware/fileserver.go b/middleware/fileserver.go
index d8c59b2ea..80cf6f841 100644
--- a/middleware/fileserver.go
+++ b/middleware/fileserver.go
@@ -62,8 +62,8 @@ func (fh *fileHandler) serveFile(w http.ResponseWriter, r *http.Request, name st
 	}
 	defer f.Close()
 
-	d, err1 := f.Stat()
-	if err1 != nil {
+	d, err := f.Stat()
+	if err != nil {
 		if os.IsNotExist(err) {
 			return http.StatusNotFound, nil
 		} else if os.IsPermission(err) {
diff --git a/middleware/fileserver_test.go b/middleware/fileserver_test.go
new file mode 100644
index 000000000..c9434a7ad
--- /dev/null
+++ b/middleware/fileserver_test.go
@@ -0,0 +1,325 @@
+package middleware
+
+import (
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+var testDir = filepath.Join(os.TempDir(), "caddy_testdir")
+var customErr = errors.New("Custom Error")
+
+// testFiles is a map with relative paths to test files as keys and file content as values.
+// The map represents the following structure:
+// - $TEMP/caddy_testdir/
+// '-- file1.html
+// '-- dirwithindex/
+// '---- index.html
+// '-- dir/
+// '---- file2.html
+// '---- hidden.html
+var testFiles = map[string]string{
+	"file1.html":                                "<h1>file1.html</h1>",
+	filepath.Join("dirwithindex", "index.html"): "<h1>dirwithindex/index.html</h1>",
+	filepath.Join("dir", "file2.html"):          "<h1>dir/file2.html</h1>",
+	filepath.Join("dir", "hidden.html"):         "<h1>dir/hidden.html</h1>",
+}
+
+// TestServeHTTP covers positive scenarios when serving files.
+func TestServeHTTP(t *testing.T) {
+
+	beforeServeHttpTest(t)
+	defer afterServeHttpTest(t)
+
+	fileserver := FileServer(http.Dir(testDir), []string{"hidden.html"})
+
+	movedPermanently := "Moved Permanently"
+
+	tests := []struct {
+		url string
+
+		expectedStatus      int
+		expectedBodyContent string
+	}{
+		// Test 0 - access withoutt any path
+		{
+			url:            "https://foo",
+			expectedStatus: http.StatusNotFound,
+		},
+		// Test 1 - access root (without index.html)
+		{
+			url:            "https://foo/",
+			expectedStatus: http.StatusNotFound,
+		},
+		// Test 2 - access existing file
+		{
+			url:                 "https://foo/file1.html",
+			expectedStatus:      http.StatusOK,
+			expectedBodyContent: testFiles["file1.html"],
+		},
+		// Test 3 - access folder with index file with trailing slash
+		{
+			url:                 "https://foo/dirwithindex/",
+			expectedStatus:      http.StatusOK,
+			expectedBodyContent: testFiles[filepath.Join("dirwithindex", "index.html")],
+		},
+		// Test 4 - access folder with index file without trailing slash
+		{
+			url:                 "https://foo/dirwithindex",
+			expectedStatus:      http.StatusMovedPermanently,
+			expectedBodyContent: movedPermanently,
+		},
+		// Test 5 - access folder without index file
+		{
+			url:            "https://foo/dir/",
+			expectedStatus: http.StatusNotFound,
+		},
+		// Test 6 - access folder withtout trailing slash
+		{
+			url:                 "https://foo/dir",
+			expectedStatus:      http.StatusMovedPermanently,
+			expectedBodyContent: movedPermanently,
+		},
+		// Test 6 - access file with trailing slash
+		{
+			url:                 "https://foo/file1.html/",
+			expectedStatus:      http.StatusMovedPermanently,
+			expectedBodyContent: movedPermanently,
+		},
+		// Test 7 - access not existing path
+		{
+			url:            "https://foo/not_existing",
+			expectedStatus: http.StatusNotFound,
+		},
+		// Test 8 - access a file, marked as hidden
+		{
+			url:            "https://foo/dir/hidden.html",
+			expectedStatus: http.StatusNotFound,
+		},
+		// Test 9 - access a index file directly
+		{
+			url:                 "https://foo/dirwithindex/index.html",
+			expectedStatus:      http.StatusOK,
+			expectedBodyContent: testFiles[filepath.Join("dirwithindex", "index.html")],
+		},
+		// Test 10 - send a request with query params
+		{
+			url:                 "https://foo/dir?param1=val",
+			expectedStatus:      http.StatusMovedPermanently,
+			expectedBodyContent: movedPermanently,
+		},
+	}
+
+	for i, test := range tests {
+		responseRecorder := httptest.NewRecorder()
+		request, err := http.NewRequest("GET", test.url, strings.NewReader(""))
+		status, err := fileserver.ServeHTTP(responseRecorder, request)
+
+		// check if error matches expectations
+		if err != nil {
+			t.Errorf(getTestPrefix(i)+"Serving file at %s failed. Error was: %v", test.url, err)
+		}
+
+		// check status code
+		if test.expectedStatus != status {
+			t.Errorf(getTestPrefix(i)+"Expected status %d, found %d", test.expectedStatus, status)
+		}
+
+		// check body content
+		if !strings.Contains(responseRecorder.Body.String(), test.expectedBodyContent) {
+			t.Errorf(getTestPrefix(i)+"Expected body to contain %q, found %q", test.expectedBodyContent, responseRecorder.Body.String())
+		}
+	}
+
+}
+
+// beforeServeHttpTest creates a test directory with the structure, defined in the variable testFiles
+func beforeServeHttpTest(t *testing.T) {
+	// make the root test dir
+	err := os.Mkdir(testDir, os.ModePerm)
+	if err != nil {
+		if !os.IsExist(err) {
+			t.Fatalf("Failed to create test dir. Error was: %v", err)
+			return
+		}
+	}
+
+	for relFile, fileContent := range testFiles {
+		absFile := filepath.Join(testDir, relFile)
+
+		// make sure the parent directories exist
+		parentDir := filepath.Dir(absFile)
+		_, err = os.Stat(parentDir)
+		if err != nil {
+			os.MkdirAll(parentDir, os.ModePerm)
+		}
+
+		// now create the test files
+		f, err := os.Create(absFile)
+		if err != nil {
+			t.Fatalf("Failed to create test file %s. Error was: %v", absFile, err)
+			return
+		}
+
+		// and fill them with content
+		_, err = f.WriteString(fileContent)
+		if err != nil {
+			t.Fatalf("Failed to write to %s. Error was: %v", absFile, err)
+			return
+		}
+		f.Close()
+	}
+
+}
+
+// afterServeHttpTest removes the test dir and all its content
+func afterServeHttpTest(t *testing.T) {
+	// cleans up everything under the test dir. No need to clean the individual files.
+	err := os.RemoveAll(testDir)
+	if err != nil {
+		t.Fatalf("Failed to clean up test dir %s. Error was: %v", testDir, err)
+	}
+}
+
+// failingFS implements the http.FileSystem interface. The Open method always returns the error, assigned to err
+type failingFS struct {
+	err      error     // the error to return when Open is called
+	fileImpl http.File // inject the file implementation
+}
+
+// Open returns the assigned failingFile and error
+func (f failingFS) Open(path string) (http.File, error) {
+	return f.fileImpl, f.err
+}
+
+// failingFile implements http.File but returns a predefined error on every Stat() method call.
+type failingFile struct {
+	http.File
+	err error
+}
+
+// Stat returns nil FileInfo and the provided error on every call
+func (ff failingFile) Stat() (os.FileInfo, error) {
+	return nil, ff.err
+}
+
+// Close is noop and returns no error
+func (ff failingFile) Close() error {
+	return nil
+}
+
+// TestServeHTTPFailingFS tests error cases where the Open function fails with various errors.
+func TestServeHTTPFailingFS(t *testing.T) {
+
+	tests := []struct {
+		fsErr           error
+		expectedStatus  int
+		expectedErr     error
+		expectedHeaders map[string]string
+	}{
+		{
+			fsErr:          os.ErrNotExist,
+			expectedStatus: http.StatusNotFound,
+			expectedErr:    nil,
+		},
+		{
+			fsErr:          os.ErrPermission,
+			expectedStatus: http.StatusForbidden,
+			expectedErr:    os.ErrPermission,
+		},
+		{
+			fsErr:           customErr,
+			expectedStatus:  http.StatusServiceUnavailable,
+			expectedErr:     customErr,
+			expectedHeaders: map[string]string{"Retry-After": "5"},
+		},
+	}
+
+	for i, test := range tests {
+		// initialize a file server with the failing FileSystem
+		fileserver := FileServer(failingFS{err: test.fsErr}, nil)
+
+		// prepare the request and response
+		request, err := http.NewRequest("GET", "https://foo/", nil)
+		if err != nil {
+			t.Fatalf("Failed to build request. Error was: %v", err)
+		}
+		responseRecorder := httptest.NewRecorder()
+
+		status, actualErr := fileserver.ServeHTTP(responseRecorder, request)
+
+		// check the status
+		if status != test.expectedStatus {
+			t.Errorf(getTestPrefix(i)+"Expected status %d, found %d", test.expectedStatus, status)
+		}
+
+		// check the error
+		if actualErr != test.expectedErr {
+			t.Errorf(getTestPrefix(i)+"Expected err %v, found %v", test.expectedErr, actualErr)
+		}
+
+		// check the headers - a special case for server under load
+		if test.expectedHeaders != nil && len(test.expectedHeaders) > 0 {
+			for expectedKey, expectedVal := range test.expectedHeaders {
+				actualVal := responseRecorder.Header().Get(expectedKey)
+				if expectedVal != actualVal {
+					t.Errorf(getTestPrefix(i)+"Expected header %s: %s, found %s", expectedKey, expectedVal, actualVal)
+				}
+			}
+		}
+	}
+}
+
+// TestServeHTTPFailingStat tests error cases where the initial Open function succeeds, but the Stat method on the opened file fails.
+func TestServeHTTPFailingStat(t *testing.T) {
+
+	tests := []struct {
+		statErr        error
+		expectedStatus int
+		expectedErr    error
+	}{
+		{
+			statErr:        os.ErrNotExist,
+			expectedStatus: http.StatusNotFound,
+			expectedErr:    nil,
+		},
+		{
+			statErr:        os.ErrPermission,
+			expectedStatus: http.StatusForbidden,
+			expectedErr:    os.ErrPermission,
+		},
+		{
+			statErr:        customErr,
+			expectedStatus: http.StatusInternalServerError,
+			expectedErr:    customErr,
+		},
+	}
+
+	for i, test := range tests {
+		// initialize a file server. The FileSystem will not fail, but calls to the Stat method of the returned File object will
+		fileserver := FileServer(failingFS{err: nil, fileImpl: failingFile{err: test.statErr}}, nil)
+
+		// prepare the request and response
+		request, err := http.NewRequest("GET", "https://foo/", nil)
+		if err != nil {
+			t.Fatalf("Failed to build request. Error was: %v", err)
+		}
+		responseRecorder := httptest.NewRecorder()
+
+		status, actualErr := fileserver.ServeHTTP(responseRecorder, request)
+
+		// check the status
+		if status != test.expectedStatus {
+			t.Errorf(getTestPrefix(i)+"Expected status %d, found %d", test.expectedStatus, status)
+		}
+
+		// check the error
+		if actualErr != test.expectedErr {
+			t.Errorf(getTestPrefix(i)+"Expected err %v, found %v", test.expectedErr, actualErr)
+		}
+	}
+}