Fix task f random theme contrast

1 files changed, 35 insertions, 0 deletions

diff --git a/internal/ui/theme_test.go b/internal/ui/theme_test.go
new file mode 100644
index 0000000..5fa6955
--- /dev/null
+++ b/internal/ui/theme_test.go
@@ -0,0 +1,35 @@
+package ui
+
+import (
+	"strconv"
+	"testing"
+)
+
+func TestContrastColorUsesHighContrastForeground(t *testing.T) {
+	for bg := 0; bg < 256; bg++ {
+		fg := contrastColor(strconv.Itoa(bg))
+		if fg != "0" && fg != "15" {
+			t.Fatalf("contrastColor(%d) = %q, want black or white foreground", bg, fg)
+		}
+
+		r, g, b := xtermRGB(bg)
+		var ratio float64
+		if fg == "0" {
+			ratio = contrastRatio(r, g, b, 0, 0, 0)
+		} else {
+			ratio = contrastRatio(r, g, b, 255, 255, 255)
+		}
+		if ratio < 4.5 {
+			t.Fatalf("contrastColor(%d) = %q with contrast ratio %.2f, want >= 4.5", bg, fg, ratio)
+		}
+	}
+}
+
+func TestContrastColorFallsBackForInvalidInput(t *testing.T) {
+	tests := []string{"not-a-color", "-1", "256"}
+	for _, input := range tests {
+		if got := contrastColor(input); got != "15" {
+			t.Fatalf("contrastColor(%q) = %q, want 15", input, got)
+		}
+	}
+}