✅ Add tests for SampleSourceFile.Companion.checkSingleClass

jvm/src/test/kotlin/org/kotools/samples/internal/SampleSourceFileTest.kt

@@ -6,6 +6,54 @@ import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
 import kotlin.test.assertNotNull
 import kotlin.test.assertNull
+import kotlin.test.fail
+
+class SampleSourceFileTest {
+    @Test
+    fun `checkSingleClass should pass with a single class in it`() {
+        val name = "/sample/kotlin/Valid.kt"
+        this::class.java.getResource(name)
+            ?.toURI()
+            ?.let(::File)
+            ?.let(SampleSourceFile.Companion::orThrow)
+            ?.checkSingleClass()
+            ?: fail("'$name' file not found.")
+    }
+
+    @Test
+    fun `checkSingleClass should fail without a class`() {
+        val name = "/sample/kotlin/NoClass.kt"
+        val file: File = this::class.java.getResource(name)
+            ?.toURI()
+            ?.let(::File)
+            ?: fail("'$name' file not found.")
+        val sampleSourceFile: SampleSourceFile = SampleSourceFile.orThrow(file)
+        val actual: String? = assertFailsWith<IllegalStateException>(
+            block = sampleSourceFile::checkSingleClass
+        ).message
+        val expected: String =
+            "The '${file.name}' file should have a single class.\n" +
+                    "File location: ${file.path}"
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun `checkSingleClass should fail with multiple classes in it`() {
+        val name = "/sample/kotlin/MultipleClasses.kt"
+        val file: File = this::class.java.getResource(name)
+            ?.toURI()
+            ?.let(::File)
+            ?: fail("'$name' file not found.")
+        val sampleSourceFile: SampleSourceFile = SampleSourceFile.orThrow(file)
+        val actual: String? = assertFailsWith<IllegalStateException>(
+            block = sampleSourceFile::checkSingleClass
+        ).message
+        val expected: String =
+            "The '${file.name}' file should have a single class.\n" +
+                    "File location: ${file.path}"
+        assertEquals(expected, actual)
+    }
+}
 
 class SampleSourceFileCompanionTest {
     @Test

jvm/src/test/resources/sample/kotlin/MultipleClasses.kt

@@ -0,0 +1,5 @@
+package sample.kotlin
+
+class A
+class B
+class C

jvm/src/test/resources/sample/kotlin/NoClass.kt

@@ -0,0 +1 @@
+package sample.kotlin

jvm/src/test/resources/sample/kotlin/Valid.kt

@@ -0,0 +1,8 @@
+class HelloKotlinSample {
+    fun greet() {
+        val name = "Sample"
+        val greeting: String = greet(name)
+        val expected = "Hello $name!"
+        assertEquals(expected, greeting)
+    }
+}