fix CLEAR directive clearing test lines, with test

src/Knit.kt

@@ -294,6 +294,7 @@ fun KnitContext.knit(inputFile: File): Boolean {
                     requireSingleLine(directive)
                     require(directive.param.isEmpty()) { "$CLEAR_DIRECTIVE directive must not have parameters" }
                     codeLines.clear()
+                    testLines.clear()
                     continue@mainLoop
                 }
                 KNIT_DIRECTIVE -> {

test/TestDataTest.kt

@@ -247,6 +247,17 @@ class TestDataTest {
        )
     }
 
+    // !!! AUTOMATICALLY GENERATED BY TestDataGen. DO NOT EDIT !!!
+    @Test
+    fun testTestClear() {
+       verifyTestData(
+           "TestClear",
+           "testdata/test-clear.in.md",
+           "testdata/test-clear.in.md",
+           "testdata/test-clear.properties"
+       )
+    }
+
     // !!! AUTOMATICALLY GENERATED BY TestDataGen. DO NOT EDIT !!!
     @Test
     fun testTestHidden() {

testdata/test-clear.in.md

@@ -0,0 +1,31 @@
+
+```kotlin 
+fun main() {
+    // this code should be cleared
+}
+```
+
+```text
+this text should be cleared
+```
+
+<!--- CLEAR --> 
+<!--- TEST_NAME ClearTest --> 
+
+Here is some explanatory text
+
+```kotlin 
+fun main() {
+    println("Hello, world!")
+}
+```                         
+
+> You can get the full code [here](test-clear/example-clear-01.kt).
+
+This code prints:
+
+```text
+Hello, world!
+```
+
+<!--- TEST -->

testdata/test-clear.properties

@@ -0,0 +1,5 @@
+knit.dir=test-clear/
+knit.package=com.example
+
+test.dir=test-clear/test/
+test.package=com.example.test

testdata/test-clear/example-clear-01.kt

@@ -0,0 +1,6 @@
+// This file was automatically generated from test-basic.in.md by Knit tool. Do not edit.
+package com.example.exampleBasic01
+
+fun main() {
+    println("Hello, world!")
+}

testdata/test-clear/test/BasicTest.kt

@@ -0,0 +1,14 @@
+// This file was automatically generated from test-basic.in.md by Knit tool. Do not edit.
+package com.example.test
+
+import org.junit.Test
+import kotlinx.knit.test.*
+
+class ClearTest {
+    @Test
+    fun testExampleBasic01() {
+        captureOutput("ExampleClear01") { com.example.exampleClear01.main() }.verifyOutputLines(
+            "Hello, world!"
+        )
+    }
+}