tiff: re-organize some test cases, and make comment style consistent.

There is no code changes in this CL, just a copy/paste and some
wordsmithing.

Change-Id: I418e8aed5ab997fad4214e8049287cac4bce8bf6
Reviewed-on: https://go-review.googlesource.com/11274
Reviewed-by: Nigel Tao <nigeltao@golang.org>

 tiff/reader_test.go | 82 +++++++++++++++++++++++++++--------------------------
 1 file changed, 42 insertions(+), 40 deletions(-)

diff --git a/tiff/reader_test.go b/tiff/reader_test.go
index 83bccd7..f5c02e6 100644
--- a/tiff/reader_test.go
+++ b/tiff/reader_test.go
@@ -38,9 +38,9 @@ func load(name string) (image.Image, error) {
 	return img, nil
 }
 
-// TestNoRPS tries to decode an image that has no RowsPerStrip tag.
-// The tag is mandatory according to the spec but some software omits
-// it in the case of a single strip.
+// TestNoRPS tests decoding an image that has no RowsPerStrip tag. The tag is
+// mandatory according to the spec but some software omits it in the case of a
+// single strip.
 func TestNoRPS(t *testing.T) {
 	_, err := load("no_rps.tiff")
 	if err != nil {
@@ -48,8 +48,9 @@ func TestNoRPS(t *testing.T) {
 	}
 }
 
-// TestNoCompression tries to decode an images that has no Compression tag.
-// This tag is mandatory, but most tools interpret a missing value as no compression.
+// TestNoCompression tests decoding an image that has no Compression tag. This
+// tag is mandatory, but most tools interpret a missing value as no
+// compression.
 func TestNoCompression(t *testing.T) {
 	_, err := load("no_compress.tiff")
 	if err != nil {
@@ -176,8 +177,8 @@ func TestDecode(t *testing.T) {
 	compare(t, img0, img4)
 }
 
-// TestDecodeLZW tests that decoding a PNG image and a LZW-compressed TIFF image
-// result in the same pixel data.
+// TestDecodeLZW tests that decoding a PNG image and a LZW-compressed TIFF
+// image result in the same pixel data.
 func TestDecodeLZW(t *testing.T) {
 	img0, err := load("blue-purple-pink.png")
 	if err != nil {
@@ -236,8 +237,36 @@ func replace(src []byte, find, repl string) ([]byte, error) {
 	return dst, nil
 }
 
-// TestTileTooBig checks that we do not panic when a tile is too big compared
-// to the data available.
+// TestZeroBitsPerSample tests that an IFD with a bitsPerSample of 0 does not
+// cause a crash.
+// Issue 10711.
+func TestZeroBitsPerSample(t *testing.T) {
+	b0, err := ioutil.ReadFile(testdataDir + "bw-deflate.tiff")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Mutate the loaded image to have the problem.
+	// 02 01: tag number (tBitsPerSample)
+	// 03 00: data type (short, or uint16)
+	// 01 00 00 00: count
+	// ?? 00 00 00: value (1 -> 0)
+	b1, err := replace(b0,
+		"02 01 03 00 01 00 00 00 01 00 00 00",
+		"02 01 03 00 01 00 00 00 00 00 00 00",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = Decode(bytes.NewReader(b1))
+	if err == nil {
+		t.Fatal("Decode with 0 bits per sample: got nil error, want non-nil")
+	}
+}
+
+// TestTileTooBig tests that we do not panic when a tile is too big compared to
+// the data available.
 // Issue 10712
 func TestTileTooBig(t *testing.T) {
 	b0, err := ioutil.ReadFile(testdataDir + "video-001-tile-64x64.tiff")
@@ -283,8 +312,8 @@ func TestTileTooBig(t *testing.T) {
 	}
 }
 
-// Do not panic when image dimensions are zero, return zero-sized
-// image instead.
+// TestZeroSizedImages tests that decoding does not panic when image dimensions
+// are zero, and returns a zero-sized image instead.
 // Issue 10393.
 func TestZeroSizedImages(t *testing.T) {
 	testsizes := []struct {
@@ -308,8 +337,8 @@ func TestZeroSizedImages(t *testing.T) {
 	}
 }
 
-// TestLargeIFDEntry verifies that a large IFD entry does not cause Decode
-// to panic.
+// TestLargeIFDEntry tests that a large IFD entry does not cause Decode to
+// panic.
 // Issue 10596.
 func TestLargeIFDEntry(t *testing.T) {
 	testdata := "II*\x00\x08\x00\x00\x00\f\x000000000000" +
@@ -327,33 +356,6 @@ func TestLargeIFDEntry(t *testing.T) {
 	}
 }
 
-// TestZeroBitsPerSample verifies that an IFD with a bitsPerSample of 0 does not cause a crash.
-// Issue 10711.
-func TestZeroBitsPerSample(t *testing.T) {
-	b0, err := ioutil.ReadFile(testdataDir + "bw-deflate.tiff")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Mutate the loaded image to have the problem.
-	// 02 01: tag number (tBitsPerSample)
-	// 03 00: data type (short, or uint16)
-	// 01 00 00 00: count
-	// ?? 00 00 00: value (1 -> 0)
-	b1, err := replace(b0,
-		"02 01 03 00 01 00 00 00 01 00 00 00",
-		"02 01 03 00 01 00 00 00 00 00 00 00",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, err = Decode(bytes.NewReader(b1))
-	if err == nil {
-		t.Fatal("Decode with 0 bits per sample: got nil error, want non-nil")
-	}
-}
-
 // benchmarkDecode benchmarks the decoding of an image.
 func benchmarkDecode(b *testing.B, filename string) {
 	b.StopTimer()