1 files changed, 142 insertions, 0 deletions
diff --git a/internal/colors/colors_test.go b/internal/colors/colors_test.go
new file mode 100644
index 0000000..569d7e2
--- /dev/null
+++ b/internal/colors/colors_test.go
@@ -0,0 +1,142 @@
+package colors
+
+import (
+	"math"
+	"testing"
+)
+
+const (
+	PCmaxDelta     = 1e-8
+	AssertTemplate = "Testing '%v'. Expected %v to become: %v Got: %v"
+)
+
+type equivalentColors struct {
+	name string
+	pc   PreciseColor
+	rgb  RGB
+	cmyk CMYK
+	hsl  HSL
+}
+
+func pcDeltaOk(a, b PreciseColor) bool {
+	return math.Abs(a.R-b.R) < PCmaxDelta &&
+		math.Abs(a.G-b.G) < PCmaxDelta &&
+		math.Abs(a.B-b.B) < PCmaxDelta
+}
+
+func getEquivalents() []equivalentColors {
+	return []equivalentColors{
+		// Black & White {{{
+		{
+			"Pure White",
+			PreciseColor{1, 1, 1},
+			RGB{255, 255, 255},
+			CMYK{0, 0, 0, 0},
+			HSL{0, 0, 100},
+		},
+		{
+			"Pure Black",
+			PreciseColor{0, 0, 0},
+			RGB{0, 0, 0},
+			CMYK{0, 0, 0, 100},
+			HSL{0, 0, 0},
+		},
+		// }}}
+		// Pure RGB {{{
+		{
+			"Red",
+			PreciseColor{1, 0, 0},
+			RGB{255, 0, 0},
+			CMYK{0, 100, 100, 0},
+			HSL{0, 100, 50},
+		},
+		{
+			"Green",
+			PreciseColor{0, 1, 0},
+			RGB{0, 255, 0},
+			CMYK{100, 0, 100, 0},
+			HSL{120, 100, 50},
+		},
+		{
+			"Blue",
+			PreciseColor{0, 0, 1},
+			RGB{0, 0, 255},
+			CMYK{100, 100, 0, 0},
+			HSL{240, 100, 50},
+		},
+		// }}}
+		// Pure CMYK {{{
+		{
+			"Cyan",
+			PreciseColor{0, 1, 1},
+			RGB{0, 255, 255},
+			CMYK{100, 0, 0, 0},
+			HSL{180, 100, 50},
+		},
+		{
+			"Magenta",
+			PreciseColor{1, 0, 1},
+			RGB{255, 0, 255},
+			CMYK{0, 100, 0, 0},
+			HSL{300, 100, 50},
+		},
+		{
+			"Yellow",
+			PreciseColor{1, 1, 0},
+			RGB{255, 255, 0},
+			CMYK{0, 0, 100, 0},
+			HSL{60, 100, 50},
+		},
+		// note: Black is already tested
+		// }}}
+		// TODO: add less pure colors to test luminance and saturation better
+	}
+}
+
+func TestToPreciseColor(t *testing.T) {
+	for _, ce := range getEquivalents() {
+		target := ce.pc
+		for _, cs := range []ColorSpace{ce.rgb, ce.cmyk, ce.hsl} {
+			pc := cs.ToPrecise()
+			if !pcDeltaOk(pc, target) {
+				t.Errorf(AssertTemplate, ce.name, cs, target, pc)
+			}
+		}
+	}
+}
+
+func TestToRgb(t *testing.T) {
+	for _, ce := range getEquivalents() {
+		target := ce.rgb
+		for _, cs := range []ColorSpace{ce.pc, ce.cmyk, ce.hsl} {
+			rgb := RGB{}.FromPrecise(cs.ToPrecise()).(RGB)
+			if rgb != target {
+				t.Errorf(AssertTemplate, ce.name, cs, target, rgb)
+			}
+		}
+	}
+}
+
+func TestToCmyk(t *testing.T) {
+	for _, ce := range getEquivalents() {
+		target := ce.cmyk
+		for _, cs := range []ColorSpace{ce.pc, ce.rgb, ce.hsl} {
+			cmyk := CMYK{}.FromPrecise(cs.ToPrecise()).(CMYK)
+			if cmyk != target {
+				t.Errorf(AssertTemplate, ce.name, cs, target, cmyk)
+			}
+		}
+	}
+}
+
+func TestToHsl(t *testing.T) {
+	for _, ce := range getEquivalents() {
+		target := ce.hsl
+		for _, cs := range []ColorSpace{ce.pc, ce.rgb, ce.cmyk} {
+			hsl := HSL{}.FromPrecise(cs.ToPrecise()).(HSL)
+			if hsl != target {
+				t.Errorf(AssertTemplate, ce.name, cs, target, hsl)
+			}
+		}
+	}
+}