cargo-insta: use cargo integration tests

This allows us to leverage Cargo itself to build the cargo-insta binary,
reducing line count in the tests and in the Makefile.

Makefile

@@ -6,21 +6,12 @@ build:
 doc:
 	@RUSTC_BOOTSTRAP=1 RUSTDOCFLAGS="--cfg=docsrs" cargo doc --no-deps --all-features
 
-test: cargotest cargo-insta-tests
-
-cargo-insta-tests:
-	@echo "CARGO-INSTA INTEGRATION TESTS"
-	# Turn off CI flag so that cargo insta test behaves as we expect
-	# under normal operation
-	@cd cargo-insta/integration-tests; CI=0 cargo run
-
-cargotest:
+test:
 	@echo "CARGO TESTS"
-	@rustup component add rustfmt 2> /dev/null
-	@cargo test
-	@cargo test --all-features
-	@cargo test --no-default-features
-	@cargo test --features redactions -- --test-threads 1
+	@env CI= cargo test
+	@env CI= cargo test --all-features
+	@env CI= cargo test --no-default-features
+	@env CI= cargo test --features redactions -- --test-threads 1
 
 check-minver:
 	@echo "MINVER CHECK"

cargo-insta/Cargo.toml

@@ -27,3 +27,6 @@ syn = { version = "1.0.50", features = ["full", "visit", "extra-traits"] }
 ignore = "0.4.17"
 uuid = { version = "1.0.0", features = ["v4"] }
 tempfile = "3.5.0"
+
+[dev-dependencies]
+walkdir = "2.3.1"

cargo-insta/integration-tests/src/main.rs → cargo-insta/tests/tests.rs

@@ -3,34 +3,12 @@ use std::fs;
 use std::path::Path;
 use std::process::Command;
 
-use dircpy::CopyBuilder;
 use insta::{assert_snapshot, Settings};
 use walkdir::WalkDir;
 
 fn main() {
-    // copy new tests over
-    fs::remove_dir_all("tests").ok();
-    CopyBuilder::new("test-input", "tests")
-        .overwrite(true)
-        .run()
-        .unwrap();
-
-    // delete old build artifacts
-    Command::new("cargo")
-        .arg("clean")
-        .arg("--package=integration-tests")
-        .status()
-        .unwrap();
-
-    // make sure cargo-insta is built
-    Command::new("cargo")
-        .arg("build")
-        .current_dir("..")
-        .status()
-        .unwrap();
-
     // run tests and accept snapshots
-    Command::new("../target/debug/cargo-insta")
+    Command::new(env!("CARGO_BIN_EXE_cargo-insta"))
         .arg("test")
         .arg("--accept")
         .arg("--no-ignore")
@@ -46,11 +24,10 @@ fn main() {
             .unwrap()
             .to_str()
             .unwrap();
-        if filename.ends_with(".rs") {
+        if let Some(snapshot) = filename.strip_suffix(".rs") {
             let gen_file = Path::new("tests").join(filename);
             let mut settings = Settings::clone_current();
             settings.set_input_file(&gen_file);
-            let snapshot = &filename[..filename.len() - 3];
             settings.bind(|| {
                 assert_snapshot!(snapshot, &fs::read_to_string(gen_file).unwrap());
             });

insta/src/utils.rs

@@ -8,11 +8,7 @@ use std::{
 
 /// Are we running in in a CI environment?
 pub fn is_ci() -> bool {
-    match env::var("CI").ok().as_deref() {
-        Some("false") | Some("0") | Some("") => false,
-        None => env::var("TF_BUILD").is_ok(),
-        Some(_) => true,
-    }
+    env::var_os("CI").is_some() || env::var_os("TF_BUILD").is_some()
 }
 
 #[cfg(feature = "colors")]