Better tests for cargo_home creation

The blackbox test now tests only what it claims to test; and added a
unit test to test the specific function we expect to create the bins.

Author: rbtcollins

src/cli/self_update.rs

@@ -1092,7 +1092,7 @@ mod test {
 
     use crate::cli::common;
     use crate::dist::dist::ToolchainDesc;
-    use crate::test::with_rustup_home;
+    use crate::test::{test_dir, with_rustup_home, Env};
     use crate::{currentprocess, for_host};
 
     #[test]
@@ -1140,4 +1140,22 @@ info: default host triple is {0}
         })
         .unwrap();
     }
+
+    #[test]
+    fn install_bins_creates_cargo_home() {
+        let root_dir = test_dir().unwrap();
+        let cargo_home = root_dir.path().join("cargo");
+        let mut vars = HashMap::new();
+        vars.env("CARGO_HOME", cargo_home.to_string_lossy().to_string());
+        let tp = Box::new(currentprocess::TestProcess {
+            vars,
+            ..Default::default()
+        });
+        currentprocess::with(tp.clone(), || -> anyhow::Result<()> {
+            super::install_bins().unwrap();
+            Ok(())
+        })
+        .unwrap();
+        assert!(cargo_home.exists());
+    }
 }

tests/cli-self-upd.rs

@@ -154,11 +154,23 @@ fn install_twice() {
 }
 
 #[test]
+/// Smoke test for the entire install process when dirs need to be made :
+/// depending just on unit tests here could miss subtle dependencies being added
+/// earlier in the code, so a black-box test is needed.
 fn install_creates_cargo_home() {
-    setup(&|config| {
+    clitools::setup(Scenario::Empty, &|config| {
         remove_dir_all(&config.cargodir).unwrap();
         config.rustupdir.remove().unwrap();
-        expect_ok(config, &["rustup-init", "-y"]);
+        expect_ok(
+            config,
+            &[
+                "rustup-init",
+                "-y",
+                "--no-modify-path",
+                "--default-toolchain",
+                "none",
+            ],
+        );
         assert!(config.cargodir.exists());
     });
 }

tests/mock/clitools.rs

@@ -51,6 +51,8 @@ pub struct Config {
 // Building the mock server is slow, so use simple scenario when possible.
 #[derive(PartialEq, Copy, Clone)]
 pub enum Scenario {
+    /// No dist server content
+    Empty,
     /// Two dates, two manifests
     Full,
     /// Two dates, v2 manifests
@@ -750,6 +752,7 @@ impl Release {
 // Creates a mock dist server populated with some test data
 fn create_mock_dist_server(path: &Path, s: Scenario) {
     let chans = match s {
+        Scenario::Empty => vec![],
         Scenario::MissingComponent => vec![
             Release::new("nightly", "1.37.0", "2019-09-12", "1"),
             Release::new("nightly", "1.37.0", "2019-09-13", "2"),
@@ -808,6 +811,7 @@ fn create_mock_dist_server(path: &Path, s: Scenario) {
     };
 
     let vs = match s {
+        Scenario::Empty => vec![],
         Scenario::Full => vec![ManifestVersion::V1, ManifestVersion::V2],
         Scenario::SimpleV1 | Scenario::ArchivesV1 => vec![ManifestVersion::V1],
         Scenario::SimpleV2