os_unix_test.go: rename to os_anyos_test.go, add windows build tag

Also remove now-unsupported freebsd build tag.

src/os/os_anyos_test.go

@@ -0,0 +1,80 @@
+// +build windows darwin linux,!baremetal
+
+package os_test
+
+import (
+	. "os"
+	"strconv"
+	"testing"
+	"time"
+)
+
+func randomName() string {
+	// fastrand() does not seem available here, so fake it
+	ns := time.Now().Nanosecond()
+	pid := Getpid()
+	return strconv.FormatUint(uint64(ns^pid), 10)
+}
+
+func TestMkdir(t *testing.T) {
+	dir := "TestMkdir" + randomName()
+	Remove(dir)
+	err := Mkdir(dir, 0755)
+	defer Remove(dir)
+	if err != nil {
+		t.Errorf("Mkdir(%s, 0755) returned %v", dir, err)
+	}
+	// tests the "directory" branch of Remove
+	err = Remove(dir)
+	if err != nil {
+		t.Errorf("Remove(%s) returned %v", dir, err)
+	}
+}
+
+func writeFile(t *testing.T, fname string, flag int, text string) string {
+	f, err := OpenFile(fname, flag, 0666)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	n, err := f.WriteString(text)
+	if err != nil {
+		t.Fatalf("WriteString: %d, %v", n, err)
+	}
+	f.Close()
+	data, err := ReadFile(f.Name())
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	return string(data)
+}
+
+func TestRemove(t *testing.T) {
+	f := "TestRemove" + randomName()
+
+	err := Remove(f)
+	if err == nil {
+		t.Errorf("TestRemove: remove of nonexistent file did not fail")
+	} else {
+		// FIXME: once we drop go 1.15, switch this to fs.PathError
+		if pe, ok := err.(*PathError); !ok {
+			t.Errorf("TestRemove: expected PathError, got err %q", err.Error())
+		} else {
+			if pe.Path != f {
+				t.Errorf("TestRemove: PathError returned path %q, expected %q", pe.Path, f)
+			}
+		}
+		if !IsNotExist(err) {
+			t.Errorf("TestRemove: expected IsNotExist(err) true, got false; err %q", err.Error())
+		}
+	}
+
+	s := writeFile(t, f, O_CREATE|O_TRUNC|O_RDWR, "new")
+	if s != "new" {
+		t.Fatalf("writeFile: have %q want %q", s, "new")
+	}
+	// tests the "file" branch of Remove
+	err = Remove(f)
+	if err != nil {
+		t.Fatalf("Remove: %v", err)
+	}
+}