Add more ioutils tests.

Closes #11595

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

ioutils/writers_test.go

@@ -6,6 +6,30 @@ import (
 	"testing"
 )
 
+func TestWriteCloserWrapperClose(t *testing.T) {
+	called := false
+	writer := bytes.NewBuffer([]byte{})
+	wrapper := NewWriteCloserWrapper(writer, func() error {
+		called = true
+		return nil
+	})
+	if err := wrapper.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if !called {
+		t.Fatalf("writeCloserWrapper should have call the anonymous function.")
+	}
+}
+
+func TestNopWriteCloser(t *testing.T) {
+	writer := bytes.NewBuffer([]byte{})
+	wrapper := NopWriteCloser(writer)
+	if err := wrapper.Close(); err != nil {
+		t.Fatal("NopWriteCloser always return nil on Close.")
+	}
+
+}
+
 func TestNopWriter(t *testing.T) {
 	nw := &NopWriter{}
 	l, err := nw.Write([]byte{'c'})