diff --git a/components/tachart/test/SourcesTest.pas b/components/tachart/test/SourcesTest.pas
index 1373719a6e..45eb593212 100644
--- a/components/tachart/test/SourcesTest.pas
+++ b/components/tachart/test/SourcesTest.pas
@@ -25,8 +25,6 @@ uses
 
 type
 
-  { TIntervalListTest }
-
   { TListSourceTest }
 
   TListSourceTest = class(TTestCase)
@@ -40,6 +38,13 @@ type
     procedure DataPoint;
   end;
 
+  { TRandomSourceTest }
+
+  TRandomSourceTest = class(TTestCase)
+  published
+    procedure Extent;
+  end;
+
 implementation
 
 uses
@@ -87,9 +92,34 @@ begin
   inherited TearDown;
 end;
 
+{ TRandomSourceTest }
+
+procedure TRandomSourceTest.Extent;
+var
+  s: TRandomChartSource;
+  ext: TDoubleRect;
+begin
+  s := TRandomChartSource.Create(nil);
+  try
+    s.XMin := 10;
+    s.XMax := 20;
+    s.YMin := 5;
+    s.YMax := 6;
+    s.PointsNumber := 1000;
+    ext := s.Extent;
+    AssertEquals(10, ext.a.X);
+    AssertEquals(20, ext.b.X);
+    Assert(ext.a.Y > 5);
+    Assert(ext.b.Y < 6);
+    Assert(ext.a.Y < ext.b.Y);
+  finally
+    s.Free;
+  end;
+end;
+
 initialization
 
-  RegisterTests([TListSourceTest]);
+  RegisterTests([TListSourceTest, TRandomSourceTest]);
 
 end.