Throw an error when verify block is empty

Author: lupuuss

mokkery-runtime/src/commonMain/kotlin/dev/mokkery/internal/Exceptions.kt

@@ -54,6 +54,9 @@ internal class SingleCallInEveryBlockRequiredException(
         }
     }
 )
+internal class SuspiciousEmptyVerifyBlockException : MokkeryRuntimeException(
+    "Given 'verify' block does not contain any call to a mock. It's very suspicious and most probably caused by misuse.\n\n$noTemplatesCommonReasons"
+)
 
 private val noTemplatesCommonReasons = """
     Possible reasons:

mokkery-runtime/src/commonMain/kotlin/dev/mokkery/internal/Verify.kt

@@ -26,11 +26,13 @@ internal fun MokkeryScope.internalVerify(
 ) {
     val scope = createTemplatingScope().apply(block)
     val instances = scope.participatingInstances
+    val templates = scope.registeredTemplates
+    if (templates.isEmpty()) throw SuspiciousEmptyVerifyBlockException()
     instances.withVerifySession {
         val result = tools
             .verifierFactory
             .create(mode, instances)
-            .verify(this.unverified, scope.registeredTemplates)
+            .verify(this.unverified, templates)
         when (result) {
             is Verifier.Result.Success -> result.verified.forEach { this.markVerified(it) }
             is Verifier.Result.Failure -> {

test-mokkery/src/commonTest/kotlin/dev/mokkery/test/TemplatingTest.kt

@@ -56,6 +56,21 @@ class TemplatingTest {
         }
     }
 
+    @Test
+    fun testEmptyVerifyCall() {
+        assertFailsWithEmptyVerifyBlock {
+            verify { }
+        }
+    }
+
+    @Test
+    fun testVerifyWithNonMockCall() {
+        assertFailsWithEmptyVerifyBlock {
+            val list = listOf<Int>()
+            verify { list.size }
+        }
+    }
+
     @Test
     fun testUnwrapping() {
         val mocks = listOf(mock)
@@ -227,6 +242,20 @@ class TemplatingTest {
         )
     }
 
+    private fun assertFailsWithEmptyVerifyBlock(block: () -> Unit) {
+        assertMokkeryError(
+            expectedMessage = """
+                Given 'verify' block does not contain any call to a mock. It's very suspicious and most probably caused by misuse.
+                
+                Possible reasons:
+                * You are calling an object that is not a mock.
+                * You are calling a mock, but the member function is final.
+                * You are calling a mock, but it's an extension function instead of a member function.
+            """.trimIndent(),
+            block = block
+        )
+    }
+
     private interface SelfType {
 
         fun callWithSelf(self: SelfType): SelfType