feat(test-support): Make it easy to launch cargo

Author: epage

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

@@ -60,6 +60,7 @@ pub mod registry;
 pub mod tools;
 
 pub mod prelude {
+    pub use crate::CargoCommand;
     pub use crate::ChannelChanger;
     pub use crate::TestEnv;
 }
@@ -1229,6 +1230,19 @@ impl TestEnv for snapbox::cmd::Command {
     }
 }
 
+/// Test the cargo command
+pub trait CargoCommand {
+    fn cargo() -> Self;
+}
+
+impl CargoCommand for snapbox::cmd::Command {
+    fn cargo() -> Self {
+        Self::new(cargo_exe())
+            .with_assert(compare::assert())
+            .test_env()
+    }
+}
+
 fn split_and_add_args(p: &mut ProcessBuilder, s: &str) {
     for mut arg in s.split_whitespace() {
         if (arg.starts_with('"') && arg.ends_with('"'))