diff --git a/datatypes/src/operations/image/to_png.rs b/datatypes/src/operations/image/to_png.rs
index 6fdb134e0..83b617355 100644
--- a/datatypes/src/operations/image/to_png.rs
+++ b/datatypes/src/operations/image/to_png.rs
@@ -272,6 +272,8 @@ mod tests {
     use super::*;
     use crate::operations::image::RgbaColor;
     use crate::raster::GridIndexAccessMut;
+    use crate::test_data;
+    use crate::util::assert_image_equals;
     use std::convert::TryInto;
 
     #[test]
@@ -298,10 +300,7 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "linear_gradient.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/linear_gradient.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("colorizer/linear_gradient.png"), &image_bytes);
     }
 
     #[test]
@@ -328,9 +327,9 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "logarithmic_gradient.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/logarithmic_gradient.png") as &[u8],
-            image_bytes.as_slice()
+        assert_image_equals(
+            test_data!("colorizer/logarithmic_gradient.png"),
+            &image_bytes,
         );
     }
 
@@ -359,10 +358,7 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "palette.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/palette.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("colorizer/palette.png"), &image_bytes);
     }
 
     #[test]
@@ -378,10 +374,7 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "rgba.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/rgba.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("colorizer/rgba.png"), &image_bytes);
     }
 
     #[test]
@@ -409,10 +402,7 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "no_data_2.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/no_data.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("colorizer/no_data.png"), &image_bytes);
     }
 
     #[test]
@@ -436,9 +426,6 @@ mod tests {
 
         // crate::util::test::save_test_bytes(&image_bytes, "empty.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/colorizer/empty.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("colorizer/empty.png"), &image_bytes);
     }
 }
diff --git a/datatypes/src/util/image.rs b/datatypes/src/util/image.rs
new file mode 100644
index 000000000..881cfd9a5
--- /dev/null
+++ b/datatypes/src/util/image.rs
@@ -0,0 +1,58 @@
+use std::path::Path;
+
+/// Compare two images
+///
+/// # Panics
+/// - if the `expected` image cannot be loaded
+/// - if the `found` bytes cannot be loaded as an image
+/// - if the images differ
+///
+pub fn assert_image_equals(expected: &Path, found: &[u8]) {
+    let left_buf = std::fs::read(expected).expect("Failed to read `expected` path");
+    let left =
+        image::load_from_memory(&left_buf).expect("Failed to make image from `expected` path");
+    let right = image::load_from_memory(found).expect("Failed to make image from `found` bytes");
+
+    assert_eq!(left, right, "Images differ: {expected:?}");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Cursor;
+
+    #[test]
+    fn it_asserts_images() {
+        const PIXELS_PER_AXIS: u32 = 8;
+
+        let tmp_file = tempfile::NamedTempFile::new().unwrap();
+
+        let mut img = image::RgbaImage::new(PIXELS_PER_AXIS, PIXELS_PER_AXIS);
+        image::save_buffer_with_format(
+            tmp_file.path(),
+            &img,
+            PIXELS_PER_AXIS,
+            PIXELS_PER_AXIS,
+            image::ExtendedColorType::Rgba8,
+            image::ImageFormat::Png,
+        )
+        .unwrap();
+
+        let mut bytes: Vec<u8> = Vec::new();
+        img.write_to(&mut Cursor::new(&mut bytes), image::ImageFormat::Png)
+            .unwrap();
+
+        assert_image_equals(tmp_file.path(), &bytes);
+
+        img.put_pixel(0, 0, image::Rgba([0, 1, 2, 3]));
+
+        let mut bytes: Vec<u8> = Vec::new();
+        img.write_to(&mut Cursor::new(&mut bytes), image::ImageFormat::Png)
+            .unwrap();
+
+        std::panic::catch_unwind(|| {
+            assert_image_equals(tmp_file.path(), &bytes);
+        })
+        .unwrap_err();
+    }
+}
diff --git a/datatypes/src/util/mod.rs b/datatypes/src/util/mod.rs
index d6a0348ef..737e1359d 100644
--- a/datatypes/src/util/mod.rs
+++ b/datatypes/src/util/mod.rs
@@ -5,6 +5,7 @@ mod db_types;
 pub mod gdal;
 pub mod helpers;
 pub mod identifiers;
+mod image;
 pub mod ranges;
 mod result;
 pub mod test;
@@ -14,6 +15,7 @@ pub use self::identifiers::Identifier;
 pub use any::{AsAny, AsAnyArc};
 pub use byte_size::ByteSize;
 pub use db_types::{HashMapTextTextDbType, NotNanF64, StringPair, TextTextKeyValue};
+pub use image::assert_image_equals;
 pub use result::Result;
 use std::path::{Path, PathBuf};
 
diff --git a/operators/src/util/raster_stream_to_png.rs b/operators/src/util/raster_stream_to_png.rs
index af0f9874d..a8a9478b8 100644
--- a/operators/src/util/raster_stream_to_png.rs
+++ b/operators/src/util/raster_stream_to_png.rs
@@ -354,7 +354,8 @@ mod tests {
     use geoengine_datatypes::{
         primitives::{BandSelection, Coordinate2D, SpatialPartition2D, SpatialResolution},
         raster::{RasterDataType, TilingSpecification},
-        util::test::TestDefault,
+        test_data,
+        util::{assert_image_equals, test::TestDefault},
     };
 
     use crate::{
@@ -420,9 +421,6 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "png_from_stream.png");
 
-        assert_eq!(
-            include_bytes!("../../../test_data/raster/png/png_from_stream.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("raster/png/png_from_stream.png"), &image_bytes);
     }
 }
diff --git a/services/src/api/handlers/wms.rs b/services/src/api/handlers/wms.rs
index 623807a3b..8999d8837 100644
--- a/services/src/api/handlers/wms.rs
+++ b/services/src/api/handlers/wms.rs
@@ -492,6 +492,8 @@ mod tests {
     use geoengine_datatypes::operations::image::{Colorizer, RgbaColor};
     use geoengine_datatypes::primitives::CacheTtlSeconds;
     use geoengine_datatypes::raster::{GridShape2D, RasterDataType, TilingSpecification};
+    use geoengine_datatypes::test_data;
+    use geoengine_datatypes::util::assert_image_equals;
     use geoengine_operators::engine::{
         ExecutionContext, RasterQueryProcessor, RasterResultDescriptor,
     };
@@ -657,12 +659,9 @@ mod tests {
         .await
         .unwrap();
 
-        // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "raster_small.png");
+        // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, test_data!("wms/raster_small.png"));
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/raster_small.png") as &[u8],
-            image_bytes.as_slice()
-        );
+        assert_image_equals(test_data!("wms/raster_small.png"), &image_bytes);
     }
 
     /// override the pixel size since this test was designed for 600 x 600 pixel tiles
@@ -714,10 +713,7 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "get_map.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/get_map.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/get_map.png"), &image_bytes);
     }
 
     #[ge_context::test]
@@ -741,10 +737,7 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "get_map_ndvi.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/get_map_ndvi.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/get_map_ndvi.png"), &image_bytes);
     }
 
     ///Actix uses serde_urlencoded inside web::Query which does not support this
@@ -765,10 +758,7 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "get_map.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/get_map.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/get_map.png"), &image_bytes);
     }
 
     #[ge_context::test(tiling_spec = "get_map_test_helper_tiling_spec")]
@@ -856,10 +846,7 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "get_map_colorizer.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/get_map_colorizer.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/get_map_colorizer.png"), &image_bytes);
     }
 
     #[ge_context::test(tiling_spec = "get_map_test_helper_tiling_spec")]
@@ -921,10 +908,7 @@ mod tests {
 
         // geoengine_datatypes::util::test::save_test_bytes(&image_bytes, "ne2_rgb_colorizer.png");
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/ne2_rgb_colorizer.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/ne2_rgb_colorizer.png"), &image_bytes);
     }
 
     #[ge_context::test(tiling_spec = "get_map_test_helper_tiling_spec")]
@@ -993,10 +977,7 @@ mod tests {
         //         .unwrap(),
         // );
 
-        assert_eq!(
-            include_bytes!("../../../../test_data/wms/ne2_rgb_colorizer_gray.png") as &[u8],
-            image_bytes
-        );
+        assert_image_equals(test_data!("wms/ne2_rgb_colorizer_gray.png"), &image_bytes);
     }
 
     #[ge_context::test]