Stop using t.Fail() and FailNow

This is bad habit and maked diagnosing test failure hard. It's not
something we want to encourag,e so remove all traces from the code.

devices/apa102/apa102_test.go

@@ -289,18 +289,21 @@ func TestRamp(t *testing.T) {
 		}
 	}
 	for i, line := range data {
-		if i != int(line.input) || line.expected != ramp(line.input, maxOut) {
-			t.Fail()
+		if i != int(line.input) {
+			t.Fatalf("expected ordered inputs; %d != %d", i, line.input)
 		}
+		if actual := ramp(line.input, maxOut); actual != line.expected {
+			t.Fatalf("%d: %v != %v", i, line.expected, actual)
 		}
-	if 0x00 != ramp(0x00, 0xFF) {
-		t.Fail()
 	}
-	if 0x21 != ramp(0x7F, 0xFF) {
-		t.Fail()
+	if v := ramp(0x00, 0xFF); v != 0x00 {
+		t.Fatal(v)
 	}
-	if 0xFF != ramp(0xFF, 0xFF) {
-		t.Fail()
+	if v := ramp(0x7F, 0xFF); v != 0x21 {
+		t.Fatal(v)
+	}
+	if v := ramp(0xFF, 0xFF); v != 0xFF {
+		t.Fatal(v)
 	}
 }
 
@@ -567,8 +570,8 @@ func TestWrites(t *testing.T) {
 }
 
 func TestDevColor(t *testing.T) {
-	if (&Dev{}).ColorModel() != color.NRGBAModel {
-		t.Fail()
+	if c := (&Dev{}).ColorModel(); c != color.NRGBAModel {
+		t.Fatal(c)
 	}
 }
 

devices/apa102/temperature_test.go

@@ -19,7 +19,7 @@ func TestToRGBFast_limits(t *testing.T) {
 func BenchmarkToRGBFast(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		if r, g, blue := toRGBFast(30000); r != 159 || g != 191 || blue != 255 {
-			b.FailNow()
+			b.Fatal(r, g, blue)
 		}
 	}
 }

devices/lepton/image14bit/intensity14_test.go

@@ -16,8 +16,11 @@ func TestIntensity14(t *testing.T) {
 	if r, g, b, a := Intensity14(0).RGBA(); r != 0 || g != r || b != r || a != 65535 {
 		t.Fatal(r, g, b, a)
 	}
-	if Intensity14(16383).String() != "Intensity14(16383)" || Intensity14(0).String() != "Intensity14(0)" {
-		t.Fail()
+	if s := Intensity14(16383).String(); s != "Intensity14(16383)" {
+		t.Fatal(s)
+	}
+	if s := Intensity14(0).String(); s != "Intensity14(0)" {
+		t.Fatal(s)
 	}
 	if Intensity14(8192) != convertIntensity14(Intensity14(8192)) {
 		t.Fatal("failed to convert Intensity14 correctly")

devices/ssd1306/image1bit/image1bit_test.go

@@ -17,11 +17,14 @@ func TestBit(t *testing.T) {
 	if r, g, b, a := Off.RGBA(); r != 0 || g != r || b != r || a != 65535 {
 		t.Fatal(r, g, b, a)
 	}
-	if On.String() != "On" || Off.String() != "Off" {
-		t.Fail()
+	if s := On.String(); s != "On" {
+		t.Fatal(s)
 	}
-	if On != convertBit(On) {
-		t.Fail()
+	if s := Off.String(); s != "Off" {
+		t.Fatal(s)
+	}
+	if b := convertBit(On); b != On {
+		t.Fatal(b)
 	}
 }
 

experimental/devices/nrzled/nrz_spi_test.go

@@ -231,14 +231,14 @@ func TestWrites(t *testing.T) {
 					t.Logf("(%d) Got:  %#02v\tWant: %#02v\n", i, got[i], tt.want[i])
 				}
 			}
-			t.Fail()
+			t.Fatal("expectation failure")
 		}
 	}
 }
 
 func TestDevColor(t *testing.T) {
-	if (&Dev{}).ColorModel() != color.NRGBAModel {
-		t.Fail()
+	if c := (&Dev{}).ColorModel(); c != color.NRGBAModel {
+		t.Fatal(c)
 	}
 }
 
@@ -342,7 +342,7 @@ func TestDraws(t *testing.T) {
 					t.Logf("(%d) Got:  %#02v\tWant: %#02v\n", i, got[i], tt.want[i])
 				}
 			}
-			t.Fail()
+			t.Fatal("expectation failure")
 		}
 	}
 }