[vcs-log][linear-bek] add a couple of tests

platform/vcs-log/graph/test/com/intellij/vcs/log/graph/linearBek/LinearBekExpandTest.kt

@@ -19,7 +19,6 @@ import com.intellij.vcs.log.graph.TestGraphBuilder
 import com.intellij.vcs.log.graph.api.elements.GraphEdge
 import com.intellij.vcs.log.graph.api.elements.GraphEdgeType
 import org.junit.Test
-import kotlin.test.assertTrue
 
 class LinearBekExpandTest {
   fun runTest(beforeLinearBekBuilder: TestGraphBuilder.() -> Unit, afterExpansionBuilder: TestGraphBuilder.() -> Unit, fromNodeToExpand: Int, toNodeToExpand: Int) {
@@ -146,4 +145,29 @@ class LinearBekExpandTest {
       9()
     }, afterLinearBek)
   }
+
+  /*
+  0
+  |\
+  | 1
+  | |\
+  |/ 2
+  3 /
+  |/
+  4
+  */
+  Test fun replaceDottedEdgeTest() {
+    val builder: TestGraphBuilder.() -> Unit = {
+      0(3, 1)
+      1(3, 2)
+      2(4)
+      3(4)
+      4()
+    }
+    val afterLinearBek = runLinearBek(builder)
+
+    afterLinearBek.expandEdge(GraphEdge.createNormalEdge(2, 3, GraphEdgeType.DOTTED))
+
+    assertEquals(builder, afterLinearBek)
+  }
 }

platform/vcs-log/graph/test/com/intellij/vcs/log/graph/linearBek/LinearBekTest.kt

@@ -615,4 +615,33 @@ class LinearBekTest {
     5(6.dot)
     6()
   })
+
+  /*
+  0               0
+  |\              |
+  | 1             1
+  | |\            |\
+  | | 2           | 2
+  | 3 |    -->    3 :
+  | \'            : :
+  |/|             :'
+  4 |             4
+  |/              |
+  5               5
+   */
+  Test fun crossedTailsTest() = runTest({
+    0(4, 1)
+    1(3, 2)
+    2(4)
+    3(5)
+    4(5)
+    5()
+  }, {
+    0(1)
+    1(3, 2)
+    2(4.dot)
+    3(4.dot)
+    4(5)
+    5()
+  })
 }