Refactor for readability

internal/chart/chart_test.go

@@ -0,0 +1,65 @@
+package chart
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"powerwatts/internal/store"
+)
+
+func TestFormatGermanNumber(t *testing.T) {
+	tests := map[int]string{
+		0:       "0",
+		12:      "12",
+		999:     "999",
+		1000:    "1.000",
+		10000:   "10.000",
+		1234567: "1.234.567",
+		-1000:   "-1.000",
+	}
+	for input, want := range tests {
+		if got := FormatGermanNumber(input); got != want {
+			t.Fatalf("FormatGermanNumber(%d) = %q, want %q", input, got, want)
+		}
+	}
+}
+
+func TestBuildHistoryChartEmpty(t *testing.T) {
+	chart := BuildHistoryChart(nil, 0)
+	if !strings.Contains(string(chart), "No power history yet") {
+		t.Fatalf("empty chart did not contain fallback text: %s", string(chart))
+	}
+}
+
+func TestBuildHistoryChartRendersPolyline(t *testing.T) {
+	history := []store.Sample{
+		{At: time.Date(2026, 4, 20, 0, 0, 0, 0, time.UTC), Value: 100},
+		{At: time.Date(2026, 4, 20, 6, 0, 0, 0, time.UTC), Value: 200},
+		{At: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), Value: 150},
+	}
+
+	chartHTML := BuildHistoryChart(history, 0)
+	if !strings.Contains(string(chartHTML), "<polyline") {
+		t.Fatalf("chart did not contain polyline: %s", string(chartHTML))
+	}
+	for _, want := range []string{"W", "00:00", "06:00", "12:00"} {
+		if !strings.Contains(string(chartHTML), want) {
+			t.Fatalf("chart did not include %q: %s", want, string(chartHTML))
+		}
+	}
+	if !strings.Contains(string(chartHTML), "0 W") {
+		t.Fatalf("chart did not include zero baseline: %s", string(chartHTML))
+	}
+}
+
+func TestBuildHistoryChartUsesConfiguredMax(t *testing.T) {
+	history := []store.Sample{{At: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), Value: 250}}
+	chartHTML := BuildHistoryChart(history, 1000)
+	if !strings.Contains(string(chartHTML), "1.000 W") {
+		t.Fatalf("chart did not include configured max: %s", string(chartHTML))
+	}
+	if strings.Contains(string(chartHTML), "250 W") {
+		t.Fatalf("chart unexpectedly used sample max instead of configured max: %s", string(chartHTML))
+	}
+}