diff --git a/api/src/main/java/com/javadiscord/jdi/core/api/utils/DiscordImageUtil.java b/api/src/main/java/com/javadiscord/jdi/core/api/utils/DiscordImageUtil.java
index 8ef8a3f4..de1a9cd8 100644
--- a/api/src/main/java/com/javadiscord/jdi/core/api/utils/DiscordImageUtil.java
+++ b/api/src/main/java/com/javadiscord/jdi/core/api/utils/DiscordImageUtil.java
@@ -23,7 +23,7 @@ public static String toDiscordString(Path path) throws IOException {
     }
 
     public static boolean isNotImage(Path path) {
-        return IMAGE_EXTENSIONS.contains(getExtension(path));
+        return !IMAGE_EXTENSIONS.contains(getExtension(path));
     }
 
     private static String getExtension(Path path) {
diff --git a/api/src/test/resources/file.txt b/api/src/test/resources/file.txt
new file mode 100644
index 00000000..71c5533f
--- /dev/null
+++ b/api/src/test/resources/file.txt
@@ -0,0 +1 @@
+This is just an ordinary file.
\ No newline at end of file
diff --git a/api/src/test/resources/image.jpg b/api/src/test/resources/image.jpg
new file mode 100644
index 00000000..06554645
Binary files /dev/null and b/api/src/test/resources/image.jpg differ
diff --git a/api/src/test/resources/image.png b/api/src/test/resources/image.png
new file mode 100644
index 00000000..854b2cbe
Binary files /dev/null and b/api/src/test/resources/image.png differ
diff --git a/api/src/test/unit/com/javadiscord/jdi/internal/api/utils/DiscordImageUtilTest.java b/api/src/test/unit/com/javadiscord/jdi/internal/api/utils/DiscordImageUtilTest.java
new file mode 100644
index 00000000..7abcde91
--- /dev/null
+++ b/api/src/test/unit/com/javadiscord/jdi/internal/api/utils/DiscordImageUtilTest.java
@@ -0,0 +1,52 @@
+package com.javadiscord.jdi.internal.api.utils;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.javadiscord.jdi.core.api.utils.DiscordImageUtil;
+
+import org.junit.jupiter.api.Test;
+
+import java.net.URL;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+class DiscordImageUtilTest {
+    private static final String IMAGE_JPG_BASE64 =
+            "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";
+
+    private Path getPathFromString(String path) throws Exception {
+        URL url = DiscordImageUtilTest.class.getResource(path);
+        if (url != null) {
+            return Paths.get(url.toURI());
+        }
+        return null;
+    }
+
+    @Test
+    void testBase64EncodePng() throws Exception {
+        assertEquals(
+                IMAGE_JPG_BASE64, DiscordImageUtil.base64Encode(getPathFromString("/image.jpg")));
+    }
+
+    @Test
+    void testNullImage() {
+        assertThrows(NullPointerException.class, () -> DiscordImageUtil.base64Encode(null));
+    }
+
+    @Test
+    void testToDiscordString() throws Exception {
+        String expected = String.format("data:image/jpg;base64,%s", IMAGE_JPG_BASE64);
+        assertEquals(expected, DiscordImageUtil.toDiscordString(getPathFromString("/image.jpg")));
+    }
+
+    @Test
+    void testIsNotImage() throws Exception {
+        Path txt = getPathFromString("/file.txt");
+        Path jpg = getPathFromString("/image.jpg");
+        Path png = getPathFromString("/image.png");
+
+        assertTrue(DiscordImageUtil.isNotImage(txt));
+        assertFalse(DiscordImageUtil.isNotImage(jpg));
+        assertFalse(DiscordImageUtil.isNotImage(png));
+    }
+}