diff --git a/cli/tests/cli/commands/decode.rs b/cli/tests/cli/commands/decode.rs
index 0da2a8c..2adb6c1 100644
--- a/cli/tests/cli/commands/decode.rs
+++ b/cli/tests/cli/commands/decode.rs
@@ -73,7 +73,7 @@ macro_rules! test_operation_with_data_without_nan_values_and_byte_order_options
                 .stdout(predicate::str::is_empty())
                 .stderr(predicate::str::is_empty());
 
-            let actual = utils::cat_as_bytes(&out_path)?;
+            let actual = utils::get_uncompressed(&out_path)?;
             assert_eq!(actual, $expected);
 
             Ok(())
@@ -154,7 +154,7 @@ fn decoding_run_length_packing_as_big_endian() -> Result<(), Box<dyn std::error:
             b => b.to_vec(),
         })
         .collect();
-    let actual = utils::cat_as_bytes(&out_path)?;
+    let actual = utils::get_uncompressed(&out_path)?;
     assert_eq!(actual, expected);
 
     Ok(())
@@ -189,7 +189,7 @@ macro_rules! test_operation_with_data_with_nan_values_as_little_endian {
                     b => b.to_vec(),
                 })
                 .collect();
-            let actual = utils::cat_as_bytes(&out_path)?;
+            let actual = utils::get_uncompressed(&out_path)?;
             assert_eq!(actual, expected);
 
             Ok(())
@@ -279,7 +279,7 @@ macro_rules! test_operation_with_data_without_nan_values_compared_using_simple_p
             let dig: i16 = $dig;
             let expected = $expected;
             let expected = utils::encode_le_bytes_using_simple_packing(expected, ref_val, exp, dig);
-            let actual = utils::cat_as_bytes(&out_path)?;
+            let actual = utils::get_uncompressed(&out_path)?;
             let actual = utils::encode_le_bytes_using_simple_packing(actual, ref_val, exp, dig);
             assert_eq!(actual, expected);
 
diff --git a/cli/tests/cli/utils.rs b/cli/tests/cli/utils.rs
index d3a32e2..552207d 100644
--- a/cli/tests/cli/utils.rs
+++ b/cli/tests/cli/utils.rs
@@ -5,77 +5,40 @@ use std::{
 };
 
 use tempfile::NamedTempFile;
-use xz2::bufread::XzDecoder;
 
 pub(crate) mod testdata;
 
-fn cat_to_tempfile<P>(file_path: P) -> Result<NamedTempFile, io::Error>
+fn write_uncompressed_to_tempfile<P>(file_path: P) -> Result<NamedTempFile, io::Error>
 where
     P: AsRef<Path>,
 {
-    let mut buf = Vec::new();
     let mut out = NamedTempFile::new()?;
-
-    let f = File::open(file_path)?;
-    let mut f = BufReader::new(f);
-    f.read_to_end(&mut buf)?;
+    let buf = get_uncompressed(file_path)?;
     out.write_all(&buf)?;
-
     Ok(out)
 }
 
-fn gzcat_to_tempfile<P>(file_path: P) -> Result<NamedTempFile, io::Error>
+pub(crate) fn get_uncompressed<P>(file_path: P) -> Result<Vec<u8>, io::Error>
 where
     P: AsRef<Path>,
 {
     let mut buf = Vec::new();
-    let mut out = NamedTempFile::new()?;
 
-    let f = File::open(file_path)?;
-    let f = BufReader::new(f);
-    let mut f = flate2::read::GzDecoder::new(f);
-    f.read_to_end(&mut buf)?;
-    out.write_all(&buf)?;
-
-    Ok(out)
-}
-
-fn xzcat_to_tempfile<P>(file_path: P) -> Result<NamedTempFile, io::Error>
-where
-    P: AsRef<Path>,
-{
-    let mut buf = Vec::new();
-    let mut out = NamedTempFile::new()?;
-
-    let f = File::open(file_path)?;
-    let f = BufReader::new(f);
-    let mut f = XzDecoder::new(f);
-    f.read_to_end(&mut buf)?;
-    out.write_all(&buf)?;
-
-    Ok(out)
-}
-
-fn unxz_as_bytes<P>(file_path: P) -> Result<Vec<u8>, io::Error>
-where
-    P: AsRef<Path>,
-{
-    let mut buf = Vec::new();
-
-    let f = File::open(file_path)?;
-    let f = BufReader::new(f);
-    let mut f = XzDecoder::new(f);
-    f.read_to_end(&mut buf)?;
-
-    Ok(buf)
-}
-
-pub(crate) fn cat_as_bytes(file_name: &str) -> Result<Vec<u8>, io::Error> {
-    let mut buf = Vec::new();
-
-    let f = File::open(file_name)?;
+    let f = File::open(&file_path)?;
     let mut f = BufReader::new(f);
-    f.read_to_end(&mut buf)?;
+    match file_path.as_ref().extension().map(|s| s.as_encoded_bytes()) {
+        Some(b"gz") => {
+            let mut f = flate2::read::GzDecoder::new(f);
+            f.read_to_end(&mut buf)?;
+        }
+        Some(b"xz") => {
+            let mut f = xz2::bufread::XzDecoder::new(f);
+            f.read_to_end(&mut buf)?;
+        }
+        _ => {
+            f.read_to_end(&mut buf)?;
+        }
+    };
 
     Ok(buf)
 }
diff --git a/cli/tests/cli/utils/testdata.rs b/cli/tests/cli/utils/testdata.rs
index 3dc4ea4..a532ad5 100644
--- a/cli/tests/cli/utils/testdata.rs
+++ b/cli/tests/cli/utils/testdata.rs
@@ -6,7 +6,7 @@ use std::{
 
 use tempfile::NamedTempFile;
 
-use crate::utils::{cat_to_tempfile, gzcat_to_tempfile, unxz_as_bytes, xzcat_to_tempfile};
+use crate::utils::{get_uncompressed, write_uncompressed_to_tempfile};
 
 fn testdata_dir() -> PathBuf {
     Path::new(concat!(env!("CARGO_MANIFEST_DIR"), "/..")).join("testdata")
@@ -35,7 +35,7 @@ pub(crate) mod grib2 {
     use super::*;
 
     pub(crate) fn cmc_glb() -> Result<NamedTempFile, io::Error> {
-        cat_to_tempfile(cmc_glb_file())
+        write_uncompressed_to_tempfile(cmc_glb_file())
     }
 
     fn cmc_glb_file() -> PathBuf {
@@ -46,62 +46,32 @@ pub(crate) mod grib2 {
         testdata_dir().join("icon_global_icosahedral_single-level_2021112018_000_TOT_PREC.grib2")
     }
 
-    pub(crate) fn jma_kousa() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(
-            testdata_dir()
-                .join("Z__C_RJTD_20170221120000_MSG_GPV_Gll0p5deg_Pys_B20170221120000_F2017022115-2017022212_grib2.bin.xz"),
-        )
-    }
-
-    pub(crate) fn jma_meps() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(
-            testdata_dir()
-                .join("Z__C_RJTD_20190605000000_MEPS_GPV_Rjp_L-pall_FH00-15_grib2.bin.0-20.xz"),
-        )
-    }
-
-    pub(crate) fn jma_msmguid() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(
-            testdata_dir()
-                .join("Z__C_RJTD_20190304000000_MSM_GUID_Rjp_P-all_FH03-39_Toorg_grib2.bin.xz"),
-        )
-    }
-
-    pub(crate) fn jma_tornado_nowcast() -> Result<NamedTempFile, io::Error> {
-        cat_to_tempfile(
-            testdata_dir()
-                .join("Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin"),
-        )
-    }
-
-    pub(crate) fn ncmrwf_wind_solar() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("wind_solar_ind_0.125_20240521_12Z.grib2.0.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_0_10() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("gdas.t12z.pgrb2.0p25.f000.0-10.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_12() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("gdas.t12z.pgrb2.0p25.f000.12.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_46() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("gdas.t12z.pgrb2.0p25.f000.46.xz"))
-    }
-
-    pub(crate) fn noaa_mrms() -> Result<NamedTempFile, io::Error> {
-        gzcat_to_tempfile(
-            testdata_dir().join("MRMS_ReflectivityAtLowestAltitude_00.50_20230406-120039.grib2.gz"),
-        )
-    }
-
-    pub(crate) fn noaa_ndfd_critfireo() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("ds.critfireo.bin.xz"))
-    }
-
-    pub(crate) fn noaa_ndfd_minrh() -> Result<NamedTempFile, io::Error> {
-        xzcat_to_tempfile(testdata_dir().join("ds.minrh.bin.xz"))
+    macro_rules! definitions_of_grib2_test_data {
+        ($(($name:ident, $file_name:expr),)*) => ($(
+            pub(crate) fn $name() -> Result<NamedTempFile, io::Error> {
+                write_uncompressed_to_tempfile(testdata_dir().join($file_name))
+            }
+        )*);
+    }
+
+    definitions_of_grib2_test_data! {
+        (
+            jma_kousa,
+            "Z__C_RJTD_20170221120000_MSG_GPV_Gll0p5deg_Pys_B20170221120000_F2017022115-2017022212_grib2.bin.xz"
+        ),
+        (jma_meps, "Z__C_RJTD_20190605000000_MEPS_GPV_Rjp_L-pall_FH00-15_grib2.bin.0-20.xz"),
+        (jma_msmguid, "Z__C_RJTD_20190304000000_MSM_GUID_Rjp_P-all_FH03-39_Toorg_grib2.bin.xz"),
+        (
+            jma_tornado_nowcast,
+            "Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin"
+        ),
+        (ncmrwf_wind_solar, "wind_solar_ind_0.125_20240521_12Z.grib2.0.xz"),
+        (noaa_gdas_0_10, "gdas.t12z.pgrb2.0p25.f000.0-10.xz"),
+        (noaa_gdas_12, "gdas.t12z.pgrb2.0p25.f000.12.xz"),
+        (noaa_gdas_46, "gdas.t12z.pgrb2.0p25.f000.46.xz"),
+        (noaa_mrms, "MRMS_ReflectivityAtLowestAltitude_00.50_20230406-120039.grib2.gz"),
+        (noaa_ndfd_critfireo, "ds.critfireo.bin.xz"),
+        (noaa_ndfd_minrh, "ds.minrh.bin.xz"),
     }
 
     pub(crate) fn multi_message_data(n: usize) -> Result<NamedTempFile, io::Error> {
@@ -122,75 +92,31 @@ pub(crate) mod grib2 {
 pub(crate) mod flat_binary {
     use super::*;
 
-    pub(crate) fn cmc_glb_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("cmc-glb-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn jma_kousa_be() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("kousa-wgrib2-be.bin.xz"))
-    }
-
-    pub(crate) fn jma_kousa_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("kousa-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn jma_meps_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("meps-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn jma_msmguid_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("msmguid-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn jma_tornado_nowcast_be() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("tornado-wgrib2-be.bin.xz"))
-    }
-
-    pub(crate) fn jma_tornado_nowcast_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("tornado-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn ncmrwf_wind_solar_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(
-            testdata_dir()
-                .join("gen")
-                .join("wind_solar_ind_0.125_20240521_12Z.wgrib2-le.bin.xz"),
-        )
-    }
-
-    pub(crate) fn noaa_gdas_0_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("gdas-0-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_1_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("gdas-1-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_2_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("gdas-2-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_12_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("gdas-12-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_gdas_46_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("gdas-46-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_mrms_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("mrms-wgrib2-le.bin.xz"))
-    }
-
-    pub(crate) fn noaa_ndfd_critfireo_0_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("ds.critfireo.bin.0.xz"))
-    }
-
-    pub(crate) fn noaa_ndfd_critfireo_1_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("ds.critfireo.bin.1.xz"))
-    }
-
-    pub(crate) fn noaa_ndfd_minrh_0_le() -> Result<Vec<u8>, io::Error> {
-        unxz_as_bytes(testdata_dir().join("gen").join("ds.minrh.bin.0.xz"))
+    macro_rules! definitions_of_flat_binary_test_data {
+        ($(($name:ident, $file_name:expr),)*) => ($(
+            pub(crate) fn $name() -> Result<Vec<u8>, io::Error> {
+                get_uncompressed(testdata_dir().join("gen").join($file_name))
+            }
+        )*);
+    }
+
+    definitions_of_flat_binary_test_data! {
+        (cmc_glb_le, "cmc-glb-wgrib2-le.bin.xz"),
+        (jma_kousa_be, "kousa-wgrib2-be.bin.xz"),
+        (jma_kousa_le, "kousa-wgrib2-le.bin.xz"),
+        (jma_meps_le, "meps-wgrib2-le.bin.xz"),
+        (jma_msmguid_le, "msmguid-wgrib2-le.bin.xz"),
+        (jma_tornado_nowcast_be, "tornado-wgrib2-be.bin.xz"),
+        (jma_tornado_nowcast_le, "tornado-wgrib2-le.bin.xz"),
+        (ncmrwf_wind_solar_le, "wind_solar_ind_0.125_20240521_12Z.wgrib2-le.bin.xz"),
+        (noaa_gdas_0_le, "gdas-0-wgrib2-le.bin.xz"),
+        (noaa_gdas_1_le, "gdas-1-wgrib2-le.bin.xz"),
+        (noaa_gdas_2_le, "gdas-2-wgrib2-le.bin.xz"),
+        (noaa_gdas_12_le, "gdas-12-wgrib2-le.bin.xz"),
+        (noaa_gdas_46_le, "gdas-46-wgrib2-le.bin.xz"),
+        (noaa_mrms_le, "mrms-wgrib2-le.bin.xz"),
+        (noaa_ndfd_critfireo_0_le, "ds.critfireo.bin.0.xz"),
+        (noaa_ndfd_critfireo_1_le, "ds.critfireo.bin.1.xz"),
+        (noaa_ndfd_minrh_0_le, "ds.minrh.bin.0.xz"),
     }
 }
diff --git a/src/grid/earth.rs b/src/grid/earth.rs
index da802ec..ed54f53 100644
--- a/src/grid/earth.rs
+++ b/src/grid/earth.rs
@@ -75,47 +75,34 @@ mod tests {
 
     use super::*;
 
-    fn ungz_as_bytes<P>(file_path: P) -> Result<Vec<u8>, std::io::Error>
+    fn get_uncompressed<P>(file_path: P) -> Result<Vec<u8>, std::io::Error>
     where
         P: AsRef<std::path::Path>,
     {
         let mut buf = Vec::new();
 
-        let f = File::open(file_path)?;
-        let f = BufReader::new(f);
-        let mut f = flate2::read::GzDecoder::new(f);
-        f.read_to_end(&mut buf)?;
-
-        Ok(buf)
-    }
-
-    fn unxz_as_bytes<P>(file_path: P) -> Result<Vec<u8>, std::io::Error>
-    where
-        P: AsRef<std::path::Path>,
-    {
-        let mut buf = Vec::new();
-
-        let f = File::open(file_path)?;
-        let f = BufReader::new(f);
-        let mut f = xz2::bufread::XzDecoder::new(f);
-        f.read_to_end(&mut buf)?;
-
-        Ok(buf)
-    }
-
-    fn cat_as_bytes(file_name: &str) -> Result<Vec<u8>, std::io::Error> {
-        let mut buf = Vec::new();
-
-        let f = File::open(file_name)?;
+        let f = File::open(&file_path)?;
         let mut f = BufReader::new(f);
-        f.read_to_end(&mut buf)?;
+        match file_path.as_ref().extension().map(|s| s.as_encoded_bytes()) {
+            Some(b"gz") => {
+                let mut f = flate2::read::GzDecoder::new(f);
+                f.read_to_end(&mut buf)?;
+            }
+            Some(b"xz") => {
+                let mut f = xz2::bufread::XzDecoder::new(f);
+                f.read_to_end(&mut buf)?;
+            }
+            _ => {
+                f.read_to_end(&mut buf)?;
+            }
+        };
 
         Ok(buf)
     }
 
     #[test]
     fn radii_for_shape_1() -> Result<(), Box<dyn std::error::Error>> {
-        let buf = unxz_as_bytes("testdata/ds.critfireo.bin.xz")?;
+        let buf = get_uncompressed("testdata/ds.critfireo.bin.xz")?;
         let earth_actual = EarthShapeDefinition::from_buf(&buf[0x83..]);
         let earth_expected = EarthShapeDefinition {
             shape_of_the_earth: 1,
@@ -134,7 +121,7 @@ mod tests {
 
     #[test]
     fn radii_for_shape_2() -> Result<(), Box<dyn std::error::Error>> {
-        let buf = ungz_as_bytes(
+        let buf = get_uncompressed(
             "testdata/MRMS_ReflectivityAtLowestAltitude_00.50_20230406-120039.grib2.gz",
         )?;
         let earth_actual = EarthShapeDefinition::from_buf(&buf[0x33..]);
@@ -155,7 +142,7 @@ mod tests {
 
     #[test]
     fn radii_for_shape_4() -> Result<(), Box<dyn std::error::Error>> {
-        let buf = cat_as_bytes(
+        let buf = get_uncompressed(
             "testdata/Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin",
         )?;
         let earth_actual = EarthShapeDefinition::from_buf(&buf[0x33..]);
@@ -176,7 +163,7 @@ mod tests {
 
     #[test]
     fn radii_for_shape_6() -> Result<(), Box<dyn std::error::Error>> {
-        let buf = unxz_as_bytes("testdata/gdas.t12z.pgrb2.0p25.f000.0-10.xz")?;
+        let buf = get_uncompressed("testdata/gdas.t12z.pgrb2.0p25.f000.0-10.xz")?;
         let earth_actual = EarthShapeDefinition::from_buf(&buf[0x33..]);
         let earth_expected = EarthShapeDefinition {
             shape_of_the_earth: 6,