test page_size via test dependency support

and move crate tests to their own folders

test_dependencies/Cargo.lock

@@ -107,6 +107,7 @@ dependencies = [
  "getrandom 0.1.16",
  "getrandom 0.2.7",
  "libc",
+ "page_size",
  "rand",
  "tokio",
 ]
@@ -127,6 +128,16 @@ version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "18a6dbe30758c9f83eb00cbea4ac95966305f5a7772f3f42ebfc7fc7eddbd8e1"
 
+[[package]]
+name = "page_size"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eebde548fbbf1ea81a99b128872779c437752fb99f217c45245e1a61dcd9edcd"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.12.1"

test_dependencies/Cargo.toml

@@ -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" }

tests/pass/crates/page_size.rs

@@ -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);
+}