os: add tests for operations on nil *File methods

R=shawn.p.smith, gobot, r
CC=golang-codereviews
https://golang.org/cl/46820043

diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index 14ecd958750a7f2a14764d3e2659ae896446bbb2..c2f811d882ba79ad3c1d5584863ded0d8d9d41db 100644 (file)
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -252,25 +252,11 @@ func TestReaddirnames(t *testing.T) {
        testReaddirnames(sysdir.name, sysdir.files, t)
 }
 
-func TestReaddirnamesNilFile(t *testing.T) {
-       var f *File
-       if fi, err := f.Readdirnames(1); fi != nil || err != ErrInvalid {
-               t.Errorf("Readdirnames should fail when f is nil: %v, %v", fi, err)
-       }
-}
-
 func TestReaddir(t *testing.T) {
        testReaddir(".", dot, t)
        testReaddir(sysdir.name, sysdir.files, t)
 }
 
-func TestReaddirNilFile(t *testing.T) {
-       var f *File
-       if fi, err := f.Readdir(1); fi != nil || err != ErrInvalid {
-               t.Errorf("Readdir should fail when f is nil: %v, %v", fi, err)
-       }
-}
-
 // Read the directory one entry at a time.
 func smallReaddirnames(file *File, length int, t *testing.T) []string {
        names := make([]string, length)
@@ -1305,3 +1291,35 @@ func TestKillFindProcess(t *testing.T) {
                }
        })
 }
+
+var nilFileMethodTests = []struct {
+       name string
+       f    func(*File) error
+}{
+       {"Chdir", func(f *File) error { return f.Chdir() }},
+       {"Close", func(f *File) error { return f.Close() }},
+       {"Chmod", func(f *File) error { return f.Chmod(0) }},
+       {"Chown", func(f *File) error { return f.Chown(0, 0) }},
+       {"Read", func(f *File) error { _, err := f.Read(make([]byte, 0)); return err }},
+       {"ReadAt", func(f *File) error { _, err := f.ReadAt(make([]byte, 0), 0); return err }},
+       {"Readdir", func(f *File) error { _, err := f.Readdir(1); return err }},
+       {"Readdirnames", func(f *File) error { _, err := f.Readdirnames(1); return err }},
+       {"Seek", func(f *File) error { _, err := f.Seek(0, 0); return err }},
+       {"Stat", func(f *File) error { _, err := f.Stat(); return err }},
+       {"Sync", func(f *File) error { return f.Sync() }},
+       {"Truncate", func(f *File) error { return f.Truncate(0) }},
+       {"Write", func(f *File) error { _, err := f.Write(make([]byte, 0)); return err }},
+       {"WriteAt", func(f *File) error { _, err := f.WriteAt(make([]byte, 0), 0); return err }},
+       {"WriteString", func(f *File) error { _, err := f.WriteString(""); return err }},
+}
+
+// Test that all File methods give ErrInvalid if the receiver is nil.
+func TestNilFileMethods(t *testing.T) {
+       for _, tt := range nilFileMethodTests {
+               var file *File
+               got := tt.f(file)
+               if got != ErrInvalid {
+                       t.Errorf("%v should fail when f is nil; got %v", tt.name, got)
+               }
+       }
+}