client: improve coverage

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

client/context_test.go

@@ -14,9 +14,25 @@ func TestFromContext(t *testing.T) {
 	}
 }
 
+func TestFromNilContext(t *testing.T) {
+	// nolint: staticcheck
+	c, ok := FromContext(nil)
+	if ok || c != nil {
+		t.Fatal("FromContext not works")
+	}
+}
+
 func TestNewContext(t *testing.T) {
 	ctx := NewContext(context.TODO(), NewClient())
+	c, ok := FromContext(ctx)
+	if c == nil || !ok {
+		t.Fatal("NewContext not works")
+	}
+}
 
+func TestNewNilContext(t *testing.T) {
+	// nolint: staticcheck
+	ctx := NewContext(nil, NewClient())
 	c, ok := FromContext(ctx)
 	if c == nil || !ok {
 		t.Fatal("NewContext not works")