1 files changed, 93 insertions, 0 deletions
diff --git a/src/io/fs/readdir_test.go b/src/io/fs/readdir_test.go
new file mode 100644
index 0000000..a2b2c12
--- /dev/null
+++ b/src/io/fs/readdir_test.go
@@ -0,0 +1,93 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fs_test
+
+import (
+	. "io/fs"
+	"os"
+	"testing"
+	"testing/fstest"
+	"time"
+)
+
+type readDirOnly struct{ ReadDirFS }
+
+func (readDirOnly) Open(name string) (File, error) { return nil, ErrNotExist }
+
+func TestReadDir(t *testing.T) {
+	check := func(desc string, dirs []DirEntry, err error) {
+		t.Helper()
+		if err != nil || len(dirs) != 2 || dirs[0].Name() != "hello.txt" || dirs[1].Name() != "sub" {
+			var names []string
+			for _, d := range dirs {
+				names = append(names, d.Name())
+			}
+			t.Errorf("ReadDir(%s) = %v, %v, want %v, nil", desc, names, err, []string{"hello.txt", "sub"})
+		}
+	}
+
+	// Test that ReadDir uses the method when present.
+	dirs, err := ReadDir(readDirOnly{testFsys}, ".")
+	check("readDirOnly", dirs, err)
+
+	// Test that ReadDir uses Open when the method is not present.
+	dirs, err = ReadDir(openOnly{testFsys}, ".")
+	check("openOnly", dirs, err)
+
+	// Test that ReadDir on Sub of . works (sub_test checks non-trivial subs).
+	sub, err := Sub(testFsys, ".")
+	if err != nil {
+		t.Fatal(err)
+	}
+	dirs, err = ReadDir(sub, ".")
+	check("sub(.)", dirs, err)
+}
+
+func TestFileInfoToDirEntry(t *testing.T) {
+	testFs := fstest.MapFS{
+		"notadir.txt": {
+			Data:    []byte("hello, world"),
+			Mode:    0,
+			ModTime: time.Now(),
+			Sys:     &sysValue,
+		},
+		"adir": {
+			Data:    nil,
+			Mode:    os.ModeDir,
+			ModTime: time.Now(),
+			Sys:     &sysValue,
+		},
+	}
+
+	tests := []struct {
+		path     string
+		wantMode FileMode
+		wantDir  bool
+	}{
+		{path: "notadir.txt", wantMode: 0, wantDir: false},
+		{path: "adir", wantMode: os.ModeDir, wantDir: true},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.path, func(t *testing.T) {
+			fi, err := Stat(testFs, test.path)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			dirEntry := FileInfoToDirEntry(fi)
+			if g, w := dirEntry.Type(), test.wantMode; g != w {
+				t.Errorf("FileMode mismatch: got=%v, want=%v", g, w)
+			}
+			if g, w := dirEntry.Name(), test.path; g != w {
+				t.Errorf("Name mismatch: got=%v, want=%v", g, w)
+			}
+			if g, w := dirEntry.IsDir(), test.wantDir; g != w {
+				t.Errorf("IsDir mismatch: got=%v, want=%v", g, w)
+			}
+		})
+	}
+}