Auto merge of #10738 - arlosi:auth-testingonly, r=ehuss

Improve testing framework for http registries

Improve integration of the http server introduced by the http-registry feature.

The same HTTP server is used for serving downloads, the index, and the API within the test framework.

This makes it easier to write tests that deal with authentication and http registries.

Most of this change is pulled from #10592. Getting it in separately should make the other change easier to review.

r? `@Eh2406`

Author: bors

crates/cargo-test-support/src/lib.rs

@@ -569,6 +569,12 @@ impl Execs {
         self
     }
 
+    /// Writes the given lines to stdin.
+    pub fn with_stdin<S: ToString>(&mut self, expected: S) -> &mut Self {
+        self.expect_stdin = Some(expected.to_string());
+        self
+    }
+
     /// Verifies the exit code from the process.
     ///
     /// This is not necessary if the expected exit code is `0`.
@@ -820,7 +826,10 @@ impl Execs {
     #[track_caller]
     pub fn run(&mut self) {
         self.ran = true;
-        let p = (&self.process_builder).clone().unwrap();
+        let mut p = (&self.process_builder).clone().unwrap();
+        if let Some(stdin) = self.expect_stdin.take() {
+            p.stdin(stdin);
+        }
         if let Err(e) = self.match_process(&p) {
             panic_error(&format!("test failed running {}", p), e);
         }