diff --git a/assetbake/opaque_bounds_test.odin b/assetbake/opaque_bounds_test.odin
new file mode 100644
index 0000000..a5e22ba
--- /dev/null
+++ b/assetbake/opaque_bounds_test.odin
@@ -0,0 +1,46 @@
+package main
+
+import "core:testing"
+
+@(test)
+opaque_bounds_inset :: proc(t: ^testing.T) {
+	// 4x4, opaque 2x2 at (1,1)
+	pixels := make([]u8, 4 * 4 * 4)
+	defer delete(pixels)
+	for y in 1 ..= 2 {
+		for x in 1 ..= 2 {
+			i := (y * 4 + x) * 4
+			pixels[i + 3] = 255
+		}
+	}
+	x, y, w, h := opaque_bounds_rgba(pixels, 4, 4)
+	testing.expect_value(t, x, 1)
+	testing.expect_value(t, y, 1)
+	testing.expect_value(t, w, 2)
+	testing.expect_value(t, h, 2)
+}
+
+@(test)
+opaque_bounds_full :: proc(t: ^testing.T) {
+	pixels := make([]u8, 2 * 2 * 4)
+	defer delete(pixels)
+	for i := 3; i < len(pixels); i += 4 {
+		pixels[i] = 255
+	}
+	x, y, w, h := opaque_bounds_rgba(pixels, 2, 2)
+	testing.expect_value(t, x, 0)
+	testing.expect_value(t, y, 0)
+	testing.expect_value(t, w, 2)
+	testing.expect_value(t, h, 2)
+}
+
+@(test)
+opaque_bounds_empty :: proc(t: ^testing.T) {
+	pixels := make([]u8, 3 * 3 * 4)
+	defer delete(pixels)
+	x, y, w, h := opaque_bounds_rgba(pixels, 3, 3)
+	testing.expect_value(t, x, 0)
+	testing.expect_value(t, y, 0)
+	testing.expect_value(t, w, 1)
+	testing.expect_value(t, h, 1)
+}
diff --git a/engine/batching_test.odin b/engine/batching_test.odin
new file mode 100644
index 0000000..3aaeabf
--- /dev/null
+++ b/engine/batching_test.odin
@@ -0,0 +1,64 @@
+package engine
+
+import "core:testing"
+import sdl "vendor:sdl3"
+
+fake_tex :: proc(id: uintptr) -> ^sdl.GPUTexture {
+	return cast(^sdl.GPUTexture)id
+}
+
+@(test)
+texture_run_len_empty_or_oob :: proc(t: ^testing.T) {
+	testing.expect_value(t, texture_run_len(nil, 0), 0)
+	list := []Queued_Sprite{}
+	testing.expect_value(t, texture_run_len(list, 0), 0)
+	list = make([]Queued_Sprite, 1)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	testing.expect_value(t, texture_run_len(list, -1), 0)
+	testing.expect_value(t, texture_run_len(list, 1), 0)
+}
+
+@(test)
+texture_run_len_single :: proc(t: ^testing.T) {
+	list := make([]Queued_Sprite, 1)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	testing.expect_value(t, texture_run_len(list, 0), 1)
+}
+
+@(test)
+texture_run_len_same_texture :: proc(t: ^testing.T) {
+	tex := fake_tex(1)
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = tex}
+	list[1] = {texture = tex}
+	list[2] = {texture = tex}
+	testing.expect_value(t, texture_run_len(list, 0), 3)
+}
+
+@(test)
+texture_run_len_breaks_on_change :: proc(t: ^testing.T) {
+	a := fake_tex(1)
+	b := fake_tex(2)
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = a}
+	list[1] = {texture = a}
+	list[2] = {texture = b}
+	testing.expect_value(t, texture_run_len(list, 0), 2)
+	testing.expect_value(t, texture_run_len(list, 2), 1)
+}
+
+@(test)
+texture_run_len_all_different :: proc(t: ^testing.T) {
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	list[1] = {texture = fake_tex(2)}
+	list[2] = {texture = fake_tex(3)}
+	testing.expect_value(t, texture_run_len(list, 0), 1)
+	testing.expect_value(t, texture_run_len(list, 1), 1)
+	testing.expect_value(t, texture_run_len(list, 2), 1)
+}
diff --git a/engine/camera_test.odin b/engine/camera_test.odin
new file mode 100644
index 0000000..3745ce8
--- /dev/null
+++ b/engine/camera_test.odin
@@ -0,0 +1,44 @@
+package engine
+
+import "core:testing"
+
+@(test)
+camera_default_values :: proc(t: ^testing.T) {
+	cam := camera_default()
+	testing.expect_value(t, cam.position, Vec2{0, 0})
+	testing.expect_value(t, cam.anchor, Vec2{0.5, 0.5})
+}
+
+@(test)
+world_to_screen_centered_identity :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {400, 500},
+		anchor   = {0.5, 0.5},
+	}
+	viewport := Vec2{800, 600}
+	screen := world_to_screen(cam, cam.position, viewport)
+	testing.expect_value(t, screen.x, f32(400))
+	testing.expect_value(t, screen.y, f32(300))
+}
+
+@(test)
+world_to_screen_origin_cam :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {0, 0},
+		anchor   = {0.5, 0.5},
+	}
+	screen := world_to_screen(cam, {10, 20}, {200, 100})
+	testing.expect_value(t, screen.x, f32(110))
+	testing.expect_value(t, screen.y, f32(70))
+}
+
+@(test)
+world_to_screen_top_left_anchor :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {5, 7},
+		anchor   = {0, 0},
+	}
+	screen := world_to_screen(cam, {15, 27}, {800, 600})
+	testing.expect_value(t, screen.x, f32(10))
+	testing.expect_value(t, screen.y, f32(20))
+}
diff --git a/engine/character_data_test.odin b/engine/character_data_test.odin
index 7e91e89..f682cd8 100644
--- a/engine/character_data_test.odin
+++ b/engine/character_data_test.odin
@@ -64,6 +64,55 @@ character_frame_rect_hit_and_miss :: proc(t: ^testing.T) {
 	testing.expect(t, !ok)
 }
 
+@(test)
+character_frame_returns_full_def :: proc(t: ^testing.T) {
+	data: Character_Data
+	data.def.clips = make(map[string]Clip_Def)
+	defer delete(data.def.clips)
+
+	frames := make([]Frame_Def, 1)
+	frames[0] = Frame_Def {
+		rect        = {10, 20, 30, 40},
+		source_size = {100, 200},
+		trim_offset = {5, 7},
+	}
+	defer delete(frames)
+
+	data.def.clips["idle"] = Clip_Def {
+		loop   = true,
+		fps    = 10,
+		frames = frames,
+	}
+
+	frame, ok := character_frame(&data, "idle", 0)
+	testing.expect(t, ok)
+	testing.expect_value(t, frame.rect, [4]int{10, 20, 30, 40})
+	testing.expect_value(t, frame.source_size, [2]int{100, 200})
+	testing.expect_value(t, frame.trim_offset, [2]int{5, 7})
+}
+
+@(test)
+character_frame_nil_and_bad_index :: proc(t: ^testing.T) {
+	_, ok := character_frame(nil, "idle", 0)
+	testing.expect(t, !ok)
+
+	data: Character_Data
+	data.def.clips = make(map[string]Clip_Def)
+	defer delete(data.def.clips)
+
+	frames := make([]Frame_Def, 1)
+	frames[0] = {rect = {1, 2, 3, 4}}
+	defer delete(frames)
+	data.def.clips["idle"] = Clip_Def{frames = frames}
+
+	_, ok = character_frame(&data, "idle", -1)
+	testing.expect(t, !ok)
+	_, ok = character_frame(&data, "idle", 1)
+	testing.expect(t, !ok)
+	_, ok = character_frame(&data, "missing", 0)
+	testing.expect(t, !ok)
+}
+
 destroy_char_def :: proc(def: ^Char_Def) {
 	if def == nil do return
 
diff --git a/engine/sprite_test.odin b/engine/sprite_test.odin
index 4135a6a..ef697e7 100644
--- a/engine/sprite_test.odin
+++ b/engine/sprite_test.odin
@@ -33,3 +33,59 @@ sprite_quad_origin_center :: proc(t: ^testing.T) {
 	testing.expect_value(t, o.x, f32(350))
 	testing.expect_value(t, o.y, f32(400))
 }
+
+@(test)
+frame_uvs_unflipped :: proc(t: ^testing.T) {
+	u0, v0, u1, v1 := frame_uvs({10, 20, 30, 40}, 100, 200, false)
+	testing.expect_value(t, u0, f32(0.1))
+	testing.expect_value(t, v0, f32(0.1))
+	testing.expect_value(t, u1, f32(0.4))
+	testing.expect_value(t, v1, f32(0.3))
+	testing.expect(t, u0 < u1)
+}
+
+@(test)
+frame_uvs_flipped :: proc(t: ^testing.T) {
+	a0, _, a1, _ := frame_uvs({10, 20, 30, 40}, 100, 200, false)
+	b0, v0, b1, v1 := frame_uvs({10, 20, 30, 40}, 100, 200, true)
+	testing.expect_value(t, b0, a1)
+	testing.expect_value(t, b1, a0)
+	testing.expect_value(t, v0, f32(0.1))
+	testing.expect_value(t, v1, f32(0.3))
+}
+
+@(test)
+sprite_feet_quad_no_flip :: proc(t: ^testing.T) {
+	// feet (400,500), source 100x200, pivot feet, trim (10,20), packed 80x160
+	x0, y0, x1, y1 := sprite_feet_quad(
+		{400, 500},
+		100,
+		200,
+		{10, 20},
+		{80, 160},
+		{0.5, 1.0},
+		false,
+	)
+	testing.expect_value(t, x0, f32(360)) // 400 - 50 + 10
+	testing.expect_value(t, y0, f32(320)) // 500 - 200 + 20
+	testing.expect_value(t, x1, f32(440))
+	testing.expect_value(t, y1, f32(480))
+}
+
+@(test)
+sprite_feet_quad_flip_x :: proc(t: ^testing.T) {
+	x0, y0, x1, y1 := sprite_feet_quad(
+		{400, 500},
+		100,
+		200,
+		{5, 20},
+		{80, 160},
+		{0.5, 1.0},
+		true,
+	)
+	// canvas_left = 350; trim_x_draw = 100 - 5 - 80 = 15 → x0 = 365
+	testing.expect_value(t, x0, f32(365))
+	testing.expect_value(t, y0, f32(320))
+	testing.expect_value(t, x1, f32(445))
+	testing.expect_value(t, y1, f32(480))
+}