add context tests

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

meter/context_test.go

@@ -0,0 +1,36 @@
+package meter
+
+import (
+	"context"
+	"testing"
+)
+
+func TestFromContext(t *testing.T) {
+	ctx := context.WithValue(context.TODO(), meterKey{}, NewMeter())
+
+	c, ok := FromContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("FromContext not works")
+	}
+}
+
+func TestNewContext(t *testing.T) {
+	ctx := NewContext(context.TODO(), NewMeter())
+
+	c, ok := FromContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("NewContext not works")
+	}
+}
+
+func TestSetOption(t *testing.T) {
+	type key struct{}
+	o := SetOption(key{}, "test")
+	opts := &Options{}
+	o(opts)
+
+	if v, ok := opts.Context.Value(key{}).(string); !ok || v == "" {
+		t.Fatal("SetOption not works")
+	}
+}
+