Adding upstream version 2.1.2.

Signed-off-by: Daniel Baumann <daniel@debian.org>

legend_test.go

@@ -0,0 +1,31 @@
+package chart
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/wcharczuk/go-chart/v2/testutil"
+)
+
+func TestLegend(t *testing.T) {
+	// replaced new assertions helper
+
+	graph := Chart{
+		Series: []Series{
+			ContinuousSeries{
+				Name:    "A test series",
+				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+			},
+		},
+	}
+
+	//note we have to do this as a separate step because we need a reference to graph
+	graph.Elements = []Renderable{
+		Legend(&graph),
+	}
+	buf := bytes.NewBuffer([]byte{})
+	err := graph.Render(PNG, buf)
+	testutil.AssertNil(t, err)
+	testutil.AssertNotZero(t, buf.Len())
+}