diff --git a/rustitch/Cargo.toml b/rustitch/Cargo.toml
index dac3b48..550bdab 100644
--- a/rustitch/Cargo.toml
+++ b/rustitch/Cargo.toml
@@ -7,3 +7,6 @@ edition = "2021"
 thiserror = "2"
 tiny-skia = "0.11"
 png = "0.17"
+
+[dev-dependencies]
+png = "0.17"
diff --git a/rustitch/tests/fixtures/JLS_Gnome Barfs.PES b/rustitch/tests/fixtures/JLS_Gnome Barfs.PES
new file mode 100644
index 0000000..406786a
Binary files /dev/null and b/rustitch/tests/fixtures/JLS_Gnome Barfs.PES differ
diff --git a/rustitch/tests/fixtures/UFront.PES b/rustitch/tests/fixtures/UFront.PES
new file mode 100644
index 0000000..3ff6dc9
Binary files /dev/null and b/rustitch/tests/fixtures/UFront.PES differ
diff --git a/rustitch/tests/fixtures/UrsulaOne.PES b/rustitch/tests/fixtures/UrsulaOne.PES
new file mode 100644
index 0000000..3a97641
Binary files /dev/null and b/rustitch/tests/fixtures/UrsulaOne.PES differ
diff --git a/rustitch/tests/pes_files.rs b/rustitch/tests/pes_files.rs
new file mode 100644
index 0000000..658416a
--- /dev/null
+++ b/rustitch/tests/pes_files.rs
@@ -0,0 +1,199 @@
+use rustitch::pes::{self, StitchCommand};
+
+const GNOME_BARFS: &[u8] = include_bytes!("fixtures/JLS_Gnome Barfs.PES");
+const URSULA_ONE: &[u8] = include_bytes!("fixtures/UrsulaOne.PES");
+const UFRONT: &[u8] = include_bytes!("fixtures/UFront.PES");
+
+// -- Header parsing ----------------------------------------------------------
+
+#[test]
+fn parse_header_gnome_barfs() {
+    let design = pes::parse(GNOME_BARFS).unwrap();
+    assert_eq!(&design.header.version, b"0100");
+}
+
+#[test]
+fn parse_header_ursula_one() {
+    let design = pes::parse(URSULA_ONE).unwrap();
+    assert_eq!(&design.header.version, b"0060");
+}
+
+#[test]
+fn parse_header_ufront() {
+    let design = pes::parse(UFRONT).unwrap();
+    assert_eq!(&design.header.version, b"0060");
+}
+
+// -- PEC color table ---------------------------------------------------------
+
+#[test]
+fn gnome_barfs_has_colors() {
+    let design = pes::parse(GNOME_BARFS).unwrap();
+    assert!(
+        design.pec_header.color_count > 0,
+        "expected at least one color"
+    );
+    assert_eq!(
+        design.pec_header.color_indices.len(),
+        design.pec_header.color_count as usize
+    );
+}
+
+#[test]
+fn ursula_one_has_colors() {
+    let design = pes::parse(URSULA_ONE).unwrap();
+    assert!(design.pec_header.color_count > 0);
+    // All color indices should be valid palette entries (0..65)
+    for &idx in &design.pec_header.color_indices {
+        assert!(
+            (idx as usize) < pes::PEC_PALETTE.len(),
+            "color index {idx} out of palette range"
+        );
+    }
+}
+
+// -- Stitch commands ---------------------------------------------------------
+
+#[test]
+fn gnome_barfs_commands_end_properly() {
+    let design = pes::parse(GNOME_BARFS).unwrap();
+    let last = design.commands.last().unwrap();
+    assert!(
+        matches!(last, StitchCommand::End),
+        "expected End command as last, got {last:?}"
+    );
+}
+
+#[test]
+fn ursula_one_commands_end_properly() {
+    let design = pes::parse(URSULA_ONE).unwrap();
+    let last = design.commands.last().unwrap();
+    assert!(
+        matches!(last, StitchCommand::End),
+        "expected End command as last, got {last:?}"
+    );
+}
+
+#[test]
+fn ufront_has_stitches() {
+    let design = pes::parse(UFRONT).unwrap();
+    let stitch_count = design
+        .commands
+        .iter()
+        .filter(|c| matches!(c, StitchCommand::Stitch { .. }))
+        .count();
+    assert!(
+        stitch_count > 100,
+        "expected many stitches, got {stitch_count}"
+    );
+}
+
+#[test]
+fn gnome_barfs_has_color_changes() {
+    let design = pes::parse(GNOME_BARFS).unwrap();
+    let changes = design
+        .commands
+        .iter()
+        .filter(|c| matches!(c, StitchCommand::ColorChange))
+        .count();
+    // Multi-color design should have at least one color change
+    assert!(changes > 0, "expected color changes, got none");
+}
+
+// -- Resolve to segments -----------------------------------------------------
+
+#[test]
+fn resolve_gnome_barfs() {
+    let design = pes::parse(GNOME_BARFS).unwrap();
+    let resolved = pes::resolve(&design).unwrap();
+
+    assert!(!resolved.segments.is_empty());
+    assert!(!resolved.colors.is_empty());
+
+    // Bounding box should be non-degenerate
+    assert!(resolved.bounds.max_x > resolved.bounds.min_x);
+    assert!(resolved.bounds.max_y > resolved.bounds.min_y);
+}
+
+#[test]
+fn resolve_ursula_one() {
+    let design = pes::parse(URSULA_ONE).unwrap();
+    let resolved = pes::resolve(&design).unwrap();
+
+    assert!(!resolved.segments.is_empty());
+    assert!(resolved.bounds.max_x > resolved.bounds.min_x);
+    assert!(resolved.bounds.max_y > resolved.bounds.min_y);
+}
+
+#[test]
+fn resolve_ufront() {
+    let design = pes::parse(UFRONT).unwrap();
+    let resolved = pes::resolve(&design).unwrap();
+
+    assert!(!resolved.segments.is_empty());
+
+    // All segment color indices should be within the resolved color list
+    let max_ci = resolved
+        .segments
+        .iter()
+        .map(|s| s.color_index)
+        .max()
+        .unwrap();
+    assert!(
+        max_ci < resolved.colors.len(),
+        "segment references color {max_ci} but only {} colors resolved",
+        resolved.colors.len()
+    );
+}
+
+// -- Full thumbnail pipeline -------------------------------------------------
+
+#[test]
+fn thumbnail_gnome_barfs_128() {
+    let png = rustitch::thumbnail(GNOME_BARFS, 128).unwrap();
+    assert_png_dimensions(&png, 128, 128);
+}
+
+#[test]
+fn thumbnail_ursula_one_256() {
+    let png = rustitch::thumbnail(URSULA_ONE, 256).unwrap();
+    assert_png_dimensions(&png, 256, 256);
+}
+
+#[test]
+fn thumbnail_ufront_64() {
+    let png = rustitch::thumbnail(UFRONT, 64).unwrap();
+    assert_png_dimensions(&png, 64, 64);
+}
+
+#[test]
+fn thumbnail_gnome_barfs_not_blank() {
+    let png = rustitch::thumbnail(GNOME_BARFS, 128).unwrap();
+    let pixels = decode_png_pixels(&png);
+    // At least some pixels should have non-zero alpha (not fully transparent)
+    let opaque_count = pixels.chunks_exact(4).filter(|px| px[3] > 0).count();
+    assert!(
+        opaque_count > 100,
+        "thumbnail looks blank, only {opaque_count} non-transparent pixels"
+    );
+}
+
+// -- Helpers -----------------------------------------------------------------
+
+fn assert_png_dimensions(png_data: &[u8], expected_w: u32, expected_h: u32) {
+    let decoder = png::Decoder::new(png_data);
+    let reader = decoder.read_info().unwrap();
+    let info = reader.info();
+    assert_eq!(info.width, expected_w, "unexpected PNG width");
+    assert_eq!(info.height, expected_h, "unexpected PNG height");
+    assert_eq!(info.color_type, png::ColorType::Rgba);
+    assert_eq!(info.bit_depth, png::BitDepth::Eight);
+}
+
+fn decode_png_pixels(png_data: &[u8]) -> Vec<u8> {
+    let decoder = png::Decoder::new(png_data);
+    let mut reader = decoder.read_info().unwrap();
+    let mut buf = vec![0u8; reader.output_buffer_size()];
+    reader.next_frame(&mut buf).unwrap();
+    buf
+}