1 files changed, 55 insertions, 0 deletions
diff --git a/internal/render/ascii_test.go b/internal/render/ascii_test.go
new file mode 100644
index 0000000..7e6a805
--- /dev/null
+++ b/internal/render/ascii_test.go
@@ -0,0 +1,55 @@
+package render
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestASCIIIsPureASCII(t *testing.T) {
+	in := " ! Upał  stopień 1\n 14  29°   (28)   zachmurzenie  ↗\n 30°│███▄▄▁"
+	got := ASCII(in, "metric")
+	for _, r := range got {
+		if r > 127 {
+			t.Fatalf("non-ASCII %q survived in %q", r, got)
+		}
+	}
+}
+
+// Substitution runs after layout, so it must not change the character count --
+// otherwise every column to the right of a degree sign shears.
+func TestASCIIPreservesLength(t *testing.T) {
+	for _, in := range []string{
+		" 14  29°   (28)   zachmurzenie",
+		" 30°│███▄▄▁▂",
+		" godz  temp  odczuw  warunki",
+		" słońce 12h03m z 14h45m dnia",
+	} {
+		if got := ASCII(in, "metric"); len([]rune(got)) != len([]rune(in)) {
+			t.Errorf("length changed: %q (%d) -> %q (%d)",
+				in, len([]rune(in)), got, len([]rune(got)))
+		}
+	}
+}
+
+// IMGW prose already writes "30°C"; the unit letter must not be doubled.
+func TestASCIIDoesNotDoubleTheUnitInProse(t *testing.T) {
+	got := ASCII("temperatura od 30°C do 33°C", "metric")
+	if strings.Contains(got, "CC") {
+		t.Fatalf("doubled unit: %q", got)
+	}
+	if got != "temperatura od 30C do 33C" {
+		t.Fatalf("got %q", got)
+	}
+}
+
+func TestASCIIUsesFahrenheitLetterInImperial(t *testing.T) {
+	if got := ASCII("85°", "imperial"); got != "85F" {
+		t.Fatalf("got %q, want 85F", got)
+	}
+}
+
+func TestASCIIMarksUnmappedRunesRatherThanDroppingThem(t *testing.T) {
+	if got := ASCII("東京", "metric"); got != "??" {
+		t.Fatalf("got %q, want ??", got)
+	}
+}