Add a unit test for Fragment size

components/layout/lib.rs

@@ -100,3 +100,6 @@ mod text;
 mod traversal;
 mod webrender_helpers;
 mod wrapper;
+
+// For unit tests:
+pub use fragment::Fragment;

components/servo/Cargo.lock

@@ -22,6 +22,7 @@ dependencies = [
  "ipc-channel 0.2.1 (git+https://github.com/servo/ipc-channel)",
  "layers 0.2.4 (git+https://github.com/servo/rust-layers)",
  "layout 0.0.1",
+ "layout_tests 0.0.1",
  "libc 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "msg 0.0.1",
@@ -1083,6 +1084,13 @@ dependencies = [
  "webrender_traits 0.1.0 (git+https://github.com/servo/webrender_traits)",
 ]
 
+[[package]]
+name = "layout_tests"
+version = "0.0.1"
+dependencies = [
+ "layout 0.0.1",
+]
+
 [[package]]
 name = "layout_traits"
 version = "0.0.1"

components/servo/Cargo.toml

@@ -24,6 +24,9 @@ image = "0.7"
 [dev-dependencies.gfx_tests]
 path = "../../tests/unit/gfx"
 
+[dev-dependencies.layout_tests]
+path = "../../tests/unit/layout"
+
 [dev-dependencies.net_tests]
 path = "../../tests/unit/net"
 

tests/unit/layout/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "layout_tests"
+version = "0.0.1"
+authors = ["The Servo Project Developers"]
+
+[lib]
+name = "layout_tests"
+path = "lib.rs"
+doctest = false
+
+[dependencies.layout]
+path = "../../../components/layout"

tests/unit/layout/lib.rs

@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate layout;
+
+#[cfg(all(test, target_pointer_width = "64"))] mod size_of;

tests/unit/layout/size_of.rs

@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use layout::Fragment;
+use std::mem::size_of;
+
+#[test]
+fn test_size_of_fragment() {
+    let expected = 184;
+    let actual = size_of::<Fragment>();
+
+    if actual < expected {
+        panic!("Your changes have decreased the stack size of layout::fragment::Fragment \
+                from {} to {}. Good work! Please update the size in tests/layout/size_of.rs",
+                expected, actual);
+    }
+
+    if actual > expected {
+        panic!("Your changes have increased the stack size of layout::fragment::Fragment \
+                from {} to {}.  Please consider choosing a design which avoids this increase. \
+                If you feel that the increase is necessary, update the size in \
+                tests/layout/size_of.rs.",
+                expected, actual);
+    }
+}