Extend YAMLDecoder Read tests

staging/src/k8s.io/apimachinery/pkg/util/yaml/decoder_test.go

@@ -29,16 +29,28 @@ import (
 	"testing"
 )
 
-func TestYAMLDecoder(t *testing.T) {
+func TestYAMLDecoderReadBytesLength(t *testing.T) {
 	d := `---
 stuff: 1
 	test-foo: 1
 `
-	s := NewDocumentDecoder(ioutil.NopCloser(bytes.NewReader([]byte(d))))
-	b := make([]byte, len(d))
-	n, err := s.Read(b)
-	if err != nil || n != len(d) {
-		t.Fatalf("unexpected body: %d / %v", n, err)
+	testCases := []struct {
+		bufLen    int
+		expectLen int
+		expectErr error
+	}{
+		{len(d), len(d), nil},
+		{len(d) + 10, len(d), nil},
+		{len(d) - 10, len(d) - 10, io.ErrShortBuffer},
+	}
+
+	for i, testCase := range testCases {
+		r := NewDocumentDecoder(ioutil.NopCloser(bytes.NewReader([]byte(d))))
+		b := make([]byte, testCase.bufLen)
+		n, err := r.Read(b)
+		if err != testCase.expectErr || n != testCase.expectLen {
+			t.Fatalf("%d: unexpected body: %d / %v", i, n, err)
+		}
 	}
 }