test page_size via test dependency support

and move crate tests to their own folders

Author: RalfJung

test_dependencies/Cargo.lock

@@ -11,6 +11,7 @@ edition = "2021"
 # all dependencies (and their transitive ones) listed here can be used in `tests/`.
 tokio = { version = "1.0", features = ["full"] }
 libc = "0.2"
+page_size = "0.4.1"
 
 getrandom_1 = { package = "getrandom", version = "0.1" }
 getrandom_2 = { package = "getrandom", version = "0.2" }

test_dependencies/Cargo.toml

@@ -0,0 +1,6 @@
+fn main() {
+    let page_size = page_size::get();
+
+    // In particular, this checks that it is not 0.
+    assert!(page_size.is_power_of_two(), "page size not a power of two: {}", page_size);
+}