diff --git a/.gitignore b/.gitignore
index 02970349..0a8e1fb9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 bin
-.history
\ No newline at end of file
+.history
+log
diff --git a/test/sanity/basics/booleans/literals.wtest b/test/sanity/basics/booleans/literals.wtest
index bfb572c9..349eb841 100644
--- a/test/sanity/basics/booleans/literals.wtest
+++ b/test/sanity/basics/booleans/literals.wtest
@@ -75,4 +75,9 @@ describe "booleans - tests with literals" {
     assert.notThat({false}.apply() || {false}.apply())
   }
 
+  test "toString" {
+    assert.equals("true", true.toString())
+    assert.equals("false", false.toString())
+  }
+
 }
diff --git a/test/sanity/basics/numbers/operators.wtest b/test/sanity/basics/numbers/operators.wtest
index 39dcdbed..31c168cc 100644
--- a/test/sanity/basics/numbers/operators.wtest
+++ b/test/sanity/basics/numbers/operators.wtest
@@ -272,4 +272,9 @@ describe "Number operators" {
     assert.equals(1, +1)
   }
 
+  test "coerceToInteger" {
+    assert.equals(2, 2.coerceToInteger())
+    assert.equals(-1, -1.coerceToInteger())
+  }
+
 }
\ No newline at end of file
diff --git a/test/sanity/basics/numbers/roundingDecimals.wtest b/test/sanity/basics/numbers/roundingDecimals.wtest
index dbc9e9b7..54d34d58 100644
--- a/test/sanity/basics/numbers/roundingDecimals.wtest
+++ b/test/sanity/basics/numbers/roundingDecimals.wtest
@@ -88,4 +88,9 @@ describe "Decimal tests"{
     assert.equals(-1, (-1.5).round())
   }
 
+  test "coerceToInteger" {
+    assert.equals(2, 2.2.coerceToInteger())
+    assert.equals(2, 2.7.coerceToInteger())
+  }
+
 }
diff --git a/test/sanity/basics/ranges/ranges.wtest b/test/sanity/basics/ranges/ranges.wtest
index ee32d5c3..88848f07 100644
--- a/test/sanity/basics/ranges/ranges.wtest
+++ b/test/sanity/basics/ranges/ranges.wtest
@@ -100,6 +100,12 @@ describe "ranges" {
     assert.that(range.contains(anyOne))
   }
 
+  test "anyOne inverse range" {
+    const range = new Range(start= 10, end = -5,step = -7)
+    const anyOne = range.anyOne()
+    assert.that(range.contains(anyOne))
+  }
+
   test "anyOne probability" {
     const range = 0 .. 10
     range.step(2)
diff --git a/test/sanity/basics/strings/strings.wtest b/test/sanity/basics/strings/strings.wtest
index 76f88590..b38f0469 100644
--- a/test/sanity/basics/strings/strings.wtest
+++ b/test/sanity/basics/strings/strings.wtest
@@ -28,7 +28,7 @@ describe "strings" {
     assert.throwsException( { "hola".substring(null) })
   }
 
-  test "substring in first parameter fail" {
+  test "substring in first parameter should fail" {
     assert.throwsException({ "hola".substring("a") })
   }
 
@@ -36,10 +36,14 @@ describe "strings" {
     assert.throwsException( { "hola".substring(null, null) })
   }
 
-  test "substring in second parameter fail" {
+  test "substring in second parameter should fail" {
     assert.throwsException({ "hola".substring("a", "e") })
   }
 
+  test "substring with invalid index should fail" {
+    assert.throwsException({ "Hola, wollok!".substring(-1, 3) })
+  }
+
   test "greater than using null should fail" {
     assert.throwsException { "hola" > null }
   }
diff --git a/test/sanity/collections/list.wtest b/test/sanity/collections/list.wtest
index d51fc7fc..2cb424cb 100644
--- a/test/sanity/collections/list.wtest
+++ b/test/sanity/collections/list.wtest
@@ -402,4 +402,22 @@ describe "List tests" {
     assert.equals(#{}, set.difference(randomized))
   }
 
+  test "findOrElse - happy path" {
+    var encontro = true
+    const valueFound = numbers.findOrElse({ elem => elem < 22 }, { encontro = false })
+    assert.that(encontro)
+  }
+  
+  test "findOrElse - not found" {
+    var encontro = true
+    const valueFound = numbers.findOrElse({ elem => elem > 100 }, { encontro = false })
+    assert.notThat(encontro)
+  }
+
+  test "join" {
+    assert.equals([1, 2, 3].join("-"), "1-2-3")
+    assert.equals([].join("-"), "")
+  }
+
+
 }
diff --git a/test/sanity/collections/set.wtest b/test/sanity/collections/set.wtest
index d5802096..b191c178 100644
--- a/test/sanity/collections/set.wtest
+++ b/test/sanity/collections/set.wtest
@@ -183,4 +183,34 @@ describe "set tests" {
     assert.equals(#{22}, numbers)  
   }
 
+  test "findOrElse - happy path" {
+    var encontro = true
+    const valueFound = #{1, 2, 3, 4}.findOrElse({ elem => elem < 3 }, { encontro = false })
+    assert.that(encontro)
+  }
+  
+  test "findOrElse - not found" {
+    var encontro = true
+    const valueFound = #{1, 2, 3, 4}.findOrElse({ elem => elem > 100 }, { encontro = false })
+    assert.notThat(encontro)
+  }
+
+  test "max" {
+    assert.equals(5, #{1, 5, 0, -8, 3}.max())
+    assert.equals(5, #{5, 1, 0, -8, 3}.max())
+    assert.equals(5, #{1, 0, -8, 3, 5}.max())
+  }
+
+  test "clear" {
+    const unSet = #{1, 2, 3}
+    assert.equals(3, unSet.size())
+    unSet.clear()
+    assert.equals(#{}, unSet)
+  }
+
+  test "join" {
+    assert.equals(#{1, 2, 3}.join("-"), "1-2-3")
+    assert.equals(#{}.join("-"), "")
+  }
+
 }