diff --git a/src/test/ValentinaTest/tst_vabstractdetail.cpp b/src/test/ValentinaTest/tst_vabstractdetail.cpp
index 60db36b21..3022002ad 100644
--- a/src/test/ValentinaTest/tst_vabstractdetail.cpp
+++ b/src/test/ValentinaTest/tst_vabstractdetail.cpp
@@ -32,6 +32,8 @@
 #include <QPointF>
 #include <QVector>
 
+#include <QtTest>
+
 //---------------------------------------------------------------------------------------------------------------------
 TST_VAbstractDetail::TST_VAbstractDetail(QObject *parent)
     :AbstractTest(parent)
@@ -51,6 +53,15 @@ void TST_VAbstractDetail::EquidistantRemoveLoop() const
 }
 
 //---------------------------------------------------------------------------------------------------------------------
+void TST_VAbstractDetail::SumTrapezoids() const
+{
+    Case3();
+    Case4();
+    Case5();
+}
+
+//---------------------------------------------------------------------------------------------------------------------
+
 void TST_VAbstractDetail::Case1() const
 {
     const QVector<QPointF> points = InputPointsCase1(); // Input points.
@@ -78,6 +89,33 @@ void TST_VAbstractDetail::Case2() const
     Comparison(ekv, ekvOrig);
 }
 
+//---------------------------------------------------------------------------------------------------------------------
+void TST_VAbstractDetail::Case3() const
+{
+    const QVector<QPointF> points = InputPointsCase3(); // Input points.
+
+    const qreal result = VAbstractDetail::SumTrapezoids(points);
+    QVERIFY(result < 0);
+}
+
+//---------------------------------------------------------------------------------------------------------------------
+void TST_VAbstractDetail::Case4() const
+{
+    const QVector<QPointF> points = InputPointsCase4(); // Input points.
+
+    const qreal result = VAbstractDetail::SumTrapezoids(points);
+    QVERIFY(result > 0);
+}
+
+//---------------------------------------------------------------------------------------------------------------------
+void TST_VAbstractDetail::Case5() const
+{
+    const QVector<QPointF> points = InputPointsCase5(); // Input points.
+
+    const qreal result = VAbstractDetail::SumTrapezoids(points);
+    QVERIFY(result == 0);
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 QVector<QPointF> TST_VAbstractDetail::InputPointsCase1() const
 {
@@ -324,3 +362,37 @@ QVector<QPointF> TST_VAbstractDetail::OutputPointsCase2() const
 
     return points;
 }
+
+//---------------------------------------------------------------------------------------------------------------------
+QVector<QPointF> TST_VAbstractDetail::InputPointsCase3() const
+{
+    QVector<QPointF> points;
+
+    points += QPointF(35, 35);
+    points += QPointF(50, 50);
+    points += QPointF(15, 50);
+
+    return points;
+}
+
+//---------------------------------------------------------------------------------------------------------------------
+QVector<QPointF> TST_VAbstractDetail::InputPointsCase4() const
+{
+    QVector<QPointF> points;
+
+    points += QPointF(15, 15);
+    points += QPointF(15, 50);
+    points += QPointF(50, 50);
+
+    return points;
+}
+
+//---------------------------------------------------------------------------------------------------------------------
+QVector<QPointF> TST_VAbstractDetail::InputPointsCase5() const
+{
+    QVector<QPointF> points;
+
+    points += QPointF(35, 35);
+
+    return points;
+}
diff --git a/src/test/ValentinaTest/tst_vabstractdetail.h b/src/test/ValentinaTest/tst_vabstractdetail.h
index 44b729a38..83790c743 100644
--- a/src/test/ValentinaTest/tst_vabstractdetail.h
+++ b/src/test/ValentinaTest/tst_vabstractdetail.h
@@ -41,10 +41,14 @@ signals:
 
 private slots:
     void EquidistantRemoveLoop() const;
+    void SumTrapezoids() const;
 
 private:
     void Case1() const;
     void Case2() const;
+    void Case3() const;
+    void Case4() const;
+    void Case5() const;
 
     QVector<QPointF> InputPointsCase1() const;
     QVector<QPointF> OutputPointsCase1() const;
@@ -52,6 +56,10 @@ private:
     QVector<QPointF> InputPointsCase2() const;
     QVector<QPointF> OutputPointsCase2() const;
 
+    QVector<QPointF> InputPointsCase3() const;
+    QVector<QPointF> InputPointsCase4() const;
+    QVector<QPointF> InputPointsCase5() const;
+
 };
 
 #endif // TST_VABSTRACTDETAIL_H