move NativeError.kotlinCause from main to test

kmp-nativecoroutines-core/src/appleMain/kotlin/com/rickclephas/kmp/nativecoroutines/NSError.kt

@@ -26,6 +26,3 @@ internal actual fun Throwable.asNativeError(): NativeError {
     }
     return NSError.errorWithDomain("KotlinException", 0.convert(), userInfo)
 }
-
-internal actual val NativeError.kotlinCause
-    get() = this.userInfo["KotlinException"] as? Throwable

kmp-nativecoroutines-core/src/appleTest/kotlin/com/rickclephas/kmp/nativecoroutines/NSErrorTests.kt

@@ -2,20 +2,12 @@ package com.rickclephas.kmp.nativecoroutines
 
 import kotlinx.cinterop.UnsafeNumber
 import kotlinx.cinterop.convert
-import kotlin.native.concurrent.isFrozen
 import kotlin.test.*
 
-class NSErrorTests {
-
-    @Test
-    fun `ensure frozen`() {
-        val exception = RandomException()
-        assertFalse(exception.isFrozen, "Exception shouldn't be frozen yet")
-        val nsError = exception.asNativeError()
-        assertTrue(nsError.isFrozen, "NSError should be frozen")
-        assertTrue(exception.isFrozen, "Exception should be frozen")
-    }
+internal actual val NativeError.kotlinCause
+    get() = this.userInfo["KotlinException"] as? Throwable
 
+class NSErrorTests {
     @Test
     @OptIn(UnsafeNumber::class)
     fun `ensure NSError domain and code are correct`() {
@@ -32,11 +24,4 @@ class NSErrorTests {
         assertEquals(exception.message, nsError.localizedDescription,
             "Localized description isn't set to message")
     }
-
-    @Test
-    fun `ensure exception is part of user info`() {
-        val exception = RandomException()
-        val nsError = exception.asNativeError()
-        assertSame(exception, nsError.kotlinCause, "Exception isn't part of the user info")
-    }
 }

kmp-nativecoroutines-core/src/nativeCoroutinesMain/kotlin/com/rickclephas/kmp/nativecoroutines/NativeError.kt

@@ -9,5 +9,3 @@ expect class NativeError
  * Converts a [Throwable] to a [NativeError].
  */
 internal expect fun Throwable.asNativeError(): NativeError
-
-internal expect val NativeError.kotlinCause: Throwable?

kmp-nativecoroutines-core/src/nativeCoroutinesTest/kotlin/com/rickclephas/kmp/nativecoroutines/NativeErrorTests.kt

@@ -0,0 +1,27 @@
+package com.rickclephas.kmp.nativecoroutines
+
+import kotlin.native.concurrent.isFrozen
+import kotlin.test.*
+
+/**
+ * Get the [Throwable] that is represented by the given [NativeError]
+ */
+internal expect val NativeError.kotlinCause: Throwable?
+
+class NativeErrorTests {
+    @Test
+    fun `ensure frozen`() {
+        val exception = RandomException()
+        assertFalse(exception.isFrozen, "Exception shouldn't be frozen yet")
+        val nsError = exception.asNativeError()
+        assertTrue(nsError.isFrozen, "NSError should be frozen")
+        assertTrue(exception.isFrozen, "Exception should be frozen")
+    }
+
+    @Test
+    fun `ensure exception is part of user info`() {
+        val exception = RandomException()
+        val nsError = exception.asNativeError()
+        assertSame(exception, nsError.kotlinCause, "Exception isn't part of the NativeError")
+    }
+}