Tests: Use custom tests to verify operations on empty slices are no-ops.

briansmith · josephlr · commit fc29d43a226b · 2022-10-22T13:25:44.000-07:00
Modify the custom tests so that they would have detected and prevented the issue fixed in rust-random#298.
diff --git a/tests/custom.rs b/tests/custom.rs
@@ -16,6 +16,9 @@ fn len7_err() -> Error {
 }
 
 fn super_insecure_rng(buf: &mut [u8]) -> Result<(), Error> {
+    // `getrandom` guarantees it will not call any implementation if the output
+    // buffer is empty.
+    assert!(!buf.is_empty());
     // Length 7 buffers return a custom error
     if buf.len() == 7 {
         return Err(len7_err());

Original file line number	Diff line number	Diff line change
`@@ -16,6 +16,9 @@ fn len7_err() -> Error {`
`16`	`16`	`}`
`17`	`17`
`18`	`18`	`fn super_insecure_rng(buf: &mut [u8]) -> Result<(), Error> {`
	`19`	+ // `getrandom` guarantees it will not call any implementation if the output
	`20`	`+ // buffer is empty.`
	`21`	`+ assert!(!buf.is_empty());`
`19`	`22`	`// Length 7 buffers return a custom error`
`20`	`23`	`if buf.len() == 7 {`
`21`	`24`	`return Err(len7_err());`