finish converting tests to kotlin

src/test/kotlin/com/github/natche/gravatarjavaclient/avatar/GravatarAvatarRequestImageSaverTest.kt

@@ -0,0 +1,59 @@
+package com.github.natche.gravatarjavaclient.avatar
+
+import com.github.natche.gravatarjavaclient.exceptions.GravatarJavaClientException
+import com.google.common.collect.ImmutableList
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.mockito.Mockito
+import java.awt.image.BufferedImage
+import java.io.File
+
+/**
+ * Tests for the [GravatarAvatarRequestImageSaver].
+ */
+class GravatarAvatarRequestImageSaverTest {
+    /**
+     * Sets the SUPPORTED_IMAGE_FORMATS to an ArrayList containing a blank string which will cause
+     * the image write to fail. This is performed for testing coverage purposes.
+     */
+    @BeforeEach
+    fun injectBlankFormat() {
+        try {
+            val formatsField = GravatarAvatarRequestImageSaver::class.java
+                .getDeclaredField("SUPPORTED_IMAGE_FORMATS")
+            formatsField.isAccessible = true
+            @Suppress("UNCHECKED_CAST")
+            val originalList = formatsField[GravatarAvatarRequestImageSaver.INSTANCE] as ImmutableList<String>
+            val mutableList: MutableList<String> = ArrayList(originalList)
+            mutableList.add("")
+            formatsField[GravatarAvatarRequestImageSaver.INSTANCE] = ImmutableList.copyOf(mutableList)
+        } catch (e: Exception) {
+            // Swallow
+        }
+    }
+
+    /**
+     * Tests for the save to method.
+     */
+    @Test
+    fun testSaveTo() {
+        Assertions.assertThrows(
+            NullPointerException::class.java
+        ) { GravatarAvatarRequestImageSaver.INSTANCE.saveTo(null, null, null) }
+        val mockImage = Mockito.mock(BufferedImage::class.java)
+        Assertions.assertThrows(
+            NullPointerException::class.java
+        ) { GravatarAvatarRequestImageSaver.INSTANCE.saveTo(mockImage, null, null) }
+        val mockFile = Mockito.mock(File::class.java)
+        Assertions.assertThrows(
+            NullPointerException::class.java
+        ) { GravatarAvatarRequestImageSaver.INSTANCE.saveTo(mockImage, mockFile, null) }
+        Assertions.assertThrows(
+            IllegalArgumentException::class.java
+        ) { GravatarAvatarRequestImageSaver.INSTANCE.saveTo(mockImage, File("."), null) }
+        Assertions.assertThrows(
+            GravatarJavaClientException::class.java
+        ) { GravatarAvatarRequestImageSaver.INSTANCE.saveTo(mockImage, mockFile, "") }
+    }
+}