diff --git a/src/cargo/core/compiler/custom_build.rs b/src/cargo/core/compiler/custom_build.rs
index c88d2f84521..2a00cf23b92 100644
--- a/src/cargo/core/compiler/custom_build.rs
+++ b/src/cargo/core/compiler/custom_build.rs
@@ -322,7 +322,7 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoRes
         } else {
             state.running(&cmd);
             let output = if extra_verbose {
-                state.capture_output(cmd, true)
+                state.capture_output(&cmd, true)
             } else {
                 cmd.exec_with_output()
             };
diff --git a/src/cargo/core/compiler/job_queue.rs b/src/cargo/core/compiler/job_queue.rs
index 1c111f727ec..fe6012f66a1 100644
--- a/src/cargo/core/compiler/job_queue.rs
+++ b/src/cargo/core/compiler/job_queue.rs
@@ -110,7 +110,7 @@ impl<'a> JobState<'a> {
 
     pub fn capture_output(
         &self,
-        cmd: ProcessBuilder,
+        cmd: &ProcessBuilder,
         print_output: bool,
     ) -> CargoResult<Output> {
         cmd.exec_with_streaming(
diff --git a/src/cargo/core/compiler/mod.rs b/src/cargo/core/compiler/mod.rs
index 1427f958288..e64a84b9b4d 100644
--- a/src/cargo/core/compiler/mod.rs
+++ b/src/cargo/core/compiler/mod.rs
@@ -118,7 +118,7 @@ impl Executor for DefaultExecutor {
         _mode: CompileMode,
         state: &job_queue::JobState<'_>,
     ) -> CargoResult<()> {
-        state.capture_output(cmd, false).map(drop)
+        state.capture_output(&cmd, false).map(drop)
     }
 }
 
@@ -645,7 +645,7 @@ fn rustdoc<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoResult
                     false,
                 ).map(drop)
         } else if should_capture_output {
-            state.capture_output(rustdoc, false).map(drop)
+            state.capture_output(&rustdoc, false).map(drop)
         } else {
             rustdoc.exec()
         };
diff --git a/src/cargo/lib.rs b/src/cargo/lib.rs
index 511531e337f..36f64c949cb 100644
--- a/src/cargo/lib.rs
+++ b/src/cargo/lib.rs
@@ -110,7 +110,7 @@ impl fmt::Display for VersionInfo {
         if let Some(channel) = self.cfg_info.as_ref().map(|ci| &ci.release_channel) {
             if channel != "stable" {
                 write!(f, "-{}", channel)?;
-                let empty = String::from("");
+                let empty = String::new();
                 write!(f, "{}", self.pre_release.as_ref().unwrap_or(&empty))?;
             }
         };
diff --git a/src/cargo/ops/fix.rs b/src/cargo/ops/fix.rs
index 662c573c215..7bc2cd405b8 100644
--- a/src/cargo/ops/fix.rs
+++ b/src/cargo/ops/fix.rs
@@ -270,7 +270,7 @@ fn rustfix_crate(lock_addr: &str, rustc: &Path, filename: &Path, args: &FixArgs)
         rustfix_and_fix(&mut fixes, rustc, filename, args)?;
         let mut progress_yet_to_be_made = false;
         for (path, file) in fixes.files.iter_mut() {
-            if file.errors_applying_fixes.len() == 0 {
+            if file.errors_applying_fixes.is_empty() {
                 continue
             }
             // If anything was successfully fixed *and* there's at least one
@@ -523,7 +523,7 @@ impl FixArgs {
             ret.prepare_for_edition = PrepareFor::Next;
         }
         ret.idioms = env::var(IDIOMS_ENV).is_ok();
-        return ret
+        ret
     }
 
     fn apply(&self, cmd: &mut Command) {
@@ -535,10 +535,7 @@ impl FixArgs {
         if let Some(edition) = &self.enabled_edition {
             cmd.arg("--edition").arg(edition);
             if self.idioms {
-                match &edition[..] {
-                    "2018" => { cmd.arg("-Wrust-2018-idioms"); }
-                    _ => {}
-                }
+                if edition == "2018" { cmd.arg("-Wrust-2018-idioms"); }
             }
         }
         match &self.prepare_for_edition {
diff --git a/src/cargo/util/diagnostic_server.rs b/src/cargo/util/diagnostic_server.rs
index 6f309ea063e..ae9e6c1ec2d 100644
--- a/src/cargo/util/diagnostic_server.rs
+++ b/src/cargo/util/diagnostic_server.rs
@@ -199,7 +199,7 @@ guide can be found at
                     file,
                     match edition {
                         Some(s) => format!("with the {} edition", s),
-                        None => format!("without an edition"),
+                        None => "without an edition".to_string(),
                     },
                 ))?;
                 Ok(())
diff --git a/tests/testsuite/build.rs b/tests/testsuite/build.rs
index b0521c8a34c..210fbd77e58 100644
--- a/tests/testsuite/build.rs
+++ b/tests/testsuite/build.rs
@@ -1024,12 +1024,12 @@ fn cargo_compile_with_downloaded_dependency_with_offline() {
         p2.cargo("build")
             .masquerade_as_nightly_cargo()
             .arg("-Zoffline"),
-        execs().with_stderr(format!(
+        execs().with_stderr(
             "\
 [COMPILING] present_dep v1.2.3
 [COMPILING] bar v0.1.0 ([..])
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]"
-        )),
+    ),
     );
 }
 
@@ -4439,7 +4439,7 @@ fn target_edition_feature_gated() {
 
     assert_that(
         p.cargo("build").arg("-v").masquerade_as_nightly_cargo(),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 error: failed to parse manifest at `[..]`
 
@@ -4451,7 +4451,7 @@ Caused by:
 
 consider adding `cargo-features = [\"edition\"]` to the manifest
 "
-        )),
+        ),
     );
 }
 
diff --git a/tests/testsuite/concurrent.rs b/tests/testsuite/concurrent.rs
index 7c6bbeafdd1..8983aace37a 100644
--- a/tests/testsuite/concurrent.rs
+++ b/tests/testsuite/concurrent.rs
@@ -52,7 +52,7 @@ fn multiple_installs() {
 
 #[test]
 fn concurrent_installs() {
-    const LOCKED_BUILD: &'static str = "waiting for file lock on build directory";
+    const LOCKED_BUILD: &str = "waiting for file lock on build directory";
 
     pkg("foo", "0.0.1");
     pkg("bar", "0.0.1");
diff --git a/tests/testsuite/config.rs b/tests/testsuite/config.rs
index fc7d02d1f53..b712fdaaccc 100644
--- a/tests/testsuite/config.rs
+++ b/tests/testsuite/config.rs
@@ -4,6 +4,7 @@ use cargo::util::toml::{self, VecStringOrBool as VSOB};
 use cargo::CargoError;
 use support::{execs, lines_match, paths, project};
 use support::hamcrest::assert_that;
+use std::borrow::Borrow;
 use std::collections;
 use std::fs;
 
@@ -68,8 +69,9 @@ fn new_config(env: &[(&str, &str)]) -> Config {
     config
 }
 
-fn assert_error(error: CargoError, msgs: &str) {
+fn assert_error<E: Borrow<CargoError>>(error: E, msgs: &str) {
     let causes = error
+        .borrow()
         .iter_chain()
         .map(|e| e.to_string())
         .collect::<Vec<_>>()
diff --git a/tests/testsuite/corrupt_git.rs b/tests/testsuite/corrupt_git.rs
index dc219045230..7d31575aaaa 100644
--- a/tests/testsuite/corrupt_git.rs
+++ b/tests/testsuite/corrupt_git.rs
@@ -38,7 +38,7 @@ fn deleting_database_files() {
 
     let mut files = Vec::new();
     find_files(&paths::home().join(".cargo/git/db"), &mut files);
-    assert!(files.len() > 0);
+    assert!(!files.is_empty());
 
     let log = "cargo::sources::git=trace";
     for file in files {
@@ -120,7 +120,7 @@ fn deleting_checkout_files() {
         .join(".git");
     let mut files = Vec::new();
     find_files(&dir, &mut files);
-    assert!(files.len() > 0);
+    assert!(!files.is_empty());
 
     let log = "cargo::sources::git=trace";
     for file in files {
diff --git a/tests/testsuite/doc.rs b/tests/testsuite/doc.rs
index ca212bf2ff6..d6898f292dc 100644
--- a/tests/testsuite/doc.rs
+++ b/tests/testsuite/doc.rs
@@ -626,7 +626,7 @@ fn doc_same_name() {
 
 #[test]
 fn doc_target() {
-    const TARGET: &'static str = "arm-unknown-linux-gnueabihf";
+    const TARGET: &str = "arm-unknown-linux-gnueabihf";
 
     let p = project()
         .file(
diff --git a/tests/testsuite/git.rs b/tests/testsuite/git.rs
index a805fc5cf8b..59d8099820d 100644
--- a/tests/testsuite/git.rs
+++ b/tests/testsuite/git.rs
@@ -61,7 +61,7 @@ fn cargo_compile_simple_git_dep() {
              [COMPILING] dep1 v0.5.0 ({}#[..])\n\
              [COMPILING] foo v0.5.0 ({})\n\
              [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]\n",
-            path2url(git_root.clone()),
+            path2url(&git_root),
             path2url(git_root),
             path2url(root)
         )),
@@ -146,7 +146,7 @@ fn cargo_compile_offline_with_cached_git_dep() {
             rev = "{}"
             "#,
                     git_project.url(),
-                    rev1.clone()
+                    rev1
                 ),
             )
             .file("src/main.rs", "fn main(){}")
@@ -166,7 +166,7 @@ fn cargo_compile_offline_with_cached_git_dep() {
             rev = "{}"
             "#,
                 git_project.url(),
-                rev2.clone()
+                rev2
             ).as_bytes())
             .unwrap();
         assert_that(prj.cargo("build"), execs());
@@ -303,7 +303,7 @@ fn cargo_compile_git_dep_branch() {
              [COMPILING] dep1 v0.5.0 ({}?branch=branchy#[..])\n\
              [COMPILING] foo v0.5.0 ({})\n\
              [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]\n",
-            path2url(git_root.clone()),
+            path2url(&git_root),
             path2url(git_root),
             path2url(root)
         )),
@@ -376,7 +376,7 @@ fn cargo_compile_git_dep_tag() {
              [COMPILING] dep1 v0.5.0 ({}?tag=v0.1.0#[..])\n\
              [COMPILING] foo v0.5.0 ({})\n\
              [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]\n",
-            path2url(git_root.clone()),
+            path2url(&git_root),
             path2url(git_root),
             path2url(root)
         )),
@@ -2674,7 +2674,7 @@ fn invalid_git_dependency_manifest() {
              \n\
              Caused by:\n  \
              duplicate key: `categories` for key `project`",
-            path2url(git_root.clone()),
+            path2url(&git_root),
             path2url(git_root),
         )),
     );
diff --git a/tests/testsuite/init.rs b/tests/testsuite/init.rs
index 7a0f6ed95b4..43dd027fc4d 100644
--- a/tests/testsuite/init.rs
+++ b/tests/testsuite/init.rs
@@ -403,7 +403,7 @@ fn gitignore_no_newline_in_new() {
         .unwrap()
         .read_to_string(&mut contents)
         .unwrap();
-    assert!(!contents.starts_with("\n"));
+    assert!(!contents.starts_with('\n'));
 }
 
 #[test]
@@ -446,7 +446,7 @@ fn mercurial_no_newline_in_new() {
         .unwrap()
         .read_to_string(&mut contents)
         .unwrap();
-    assert!(!contents.starts_with("\n"));
+    assert!(!contents.starts_with('\n'));
 }
 
 #[test]
diff --git a/tests/testsuite/login.rs b/tests/testsuite/login.rs
index 062929a9d50..81070a335a9 100644
--- a/tests/testsuite/login.rs
+++ b/tests/testsuite/login.rs
@@ -60,7 +60,7 @@ fn check_token(expected_token: &str, registry: Option<&str>) -> bool {
             .get("registry")
             .and_then(|registry_table| registry_table.get("token"))
             .and_then(|v| match v {
-                &toml::Value::String(ref token) => Some(token.as_str().to_string()),
+                toml::Value::String(ref token) => Some(token.as_str().to_string()),
                 _ => None,
             }),
         _ => None,
diff --git a/tests/testsuite/main.rs b/tests/testsuite/main.rs
index 6b89f298006..7ec164ef00c 100644
--- a/tests/testsuite/main.rs
+++ b/tests/testsuite/main.rs
@@ -1,4 +1,6 @@
 #![deny(warnings)]
+#![cfg_attr(feature = "cargo-clippy", allow(blacklisted_name))]
+#![cfg_attr(feature = "cargo-clippy", allow(explicit_iter_loop))]
 
 extern crate bufstream;
 extern crate cargo;
diff --git a/tests/testsuite/package.rs b/tests/testsuite/package.rs
index 671eebebcd0..55fe71eb423 100644
--- a/tests/testsuite/package.rs
+++ b/tests/testsuite/package.rs
@@ -1016,7 +1016,7 @@ fn test_edition_malformed() {
 
     assert_that(
         p.cargo("build").arg("-v").masquerade_as_nightly_cargo(),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 error: failed to parse manifest at `[..]`
 
@@ -1025,8 +1025,8 @@ Caused by:
 
 Caused by:
   supported edition values are `2015` or `2018`, but `chicken` is unknown
-"
-        )),
+".to_string()
+        ),
     );
 }
 
@@ -1048,7 +1048,7 @@ fn test_edition_nightly() {
 
     assert_that(
         p.cargo("build").arg("-v").masquerade_as_nightly_cargo(),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 error: failed to parse manifest at `[..]`
 
@@ -1060,7 +1060,7 @@ Caused by:
 
 consider adding `cargo-features = [\"edition\"]` to the manifest
 "
-        )),
+        ),
     );
 }
 
diff --git a/tests/testsuite/patch.rs b/tests/testsuite/patch.rs
index cf815afc305..980f449459f 100644
--- a/tests/testsuite/patch.rs
+++ b/tests/testsuite/patch.rs
@@ -702,7 +702,7 @@ fn remove_patch() {
     File::create(p.root().join("Cargo.toml"))
         .unwrap()
         .write_all(
-            r#"
+            br#"
         [package]
         name = "foo"
         version = "0.0.1"
@@ -713,7 +713,7 @@ fn remove_patch() {
 
         [patch.crates-io]
         bar = { path = 'bar' }
-    "#.as_bytes(),
+    "#,
         )
         .unwrap();
     assert_that(p.cargo("build"), execs());
diff --git a/tests/testsuite/publish.rs b/tests/testsuite/publish.rs
index f09643f6d37..a27111a0fcc 100644
--- a/tests/testsuite/publish.rs
+++ b/tests/testsuite/publish.rs
@@ -51,9 +51,9 @@ See [..]
     // Skip the metadata payload and the size of the tarball
     let mut sz = [0; 4];
     assert_eq!(f.read(&mut sz).unwrap(), 4);
-    let sz = ((sz[0] as u32) << 0) | ((sz[1] as u32) << 8) | ((sz[2] as u32) << 16)
-        | ((sz[3] as u32) << 24);
-    f.seek(SeekFrom::Current(sz as i64 + 4)).unwrap();
+    let sz = (u32::from(sz[0]) << 0) | (u32::from(sz[1]) << 8) | (u32::from(sz[2]) << 16)
+        | (u32::from(sz[3]) << 24);
+    f.seek(SeekFrom::Current(i64::from(sz) + 4)).unwrap();
 
     // Verify the tarball
     let mut rdr = GzDecoder::new(f);
@@ -127,9 +127,9 @@ See [..]
     // Skip the metadata payload and the size of the tarball
     let mut sz = [0; 4];
     assert_eq!(f.read(&mut sz).unwrap(), 4);
-    let sz = ((sz[0] as u32) << 0) | ((sz[1] as u32) << 8) | ((sz[2] as u32) << 16)
-        | ((sz[3] as u32) << 24);
-    f.seek(SeekFrom::Current(sz as i64 + 4)).unwrap();
+    let sz = (u32::from(sz[0]) << 0) | (u32::from(sz[1]) << 8) | (u32::from(sz[2]) << 16)
+        | (u32::from(sz[3]) << 24);
+    f.seek(SeekFrom::Current(i64::from(sz) + 4)).unwrap();
 
     // Verify the tarball
     let mut rdr = GzDecoder::new(f);
@@ -205,15 +205,15 @@ See [..]
     // Skip the metadata payload and the size of the tarball
     let mut sz = [0; 4];
     assert_eq!(f.read(&mut sz).unwrap(), 4);
-    let sz = ((sz[0] as u32) << 0) | ((sz[1] as u32) << 8) | ((sz[2] as u32) << 16)
-        | ((sz[3] as u32) << 24);
-    f.seek(SeekFrom::Current(sz as i64 + 4)).unwrap();
+    let sz = (u32::from(sz[0]) << 0) | (u32::from(sz[1]) << 8) | (u32::from(sz[2]) << 16)
+        | (u32::from(sz[3]) << 24);
+    f.seek(SeekFrom::Current(i64::from(sz) + 4)).unwrap();
 
     // Verify the tarball
     let mut rdr = GzDecoder::new(f);
     assert_eq!(
         rdr.header().unwrap().filename().unwrap(),
-        "foo-0.0.1.crate".as_bytes()
+        b"foo-0.0.1.crate"
     );
     let mut contents = Vec::new();
     rdr.read_to_end(&mut contents).unwrap();
@@ -285,15 +285,15 @@ See [..]
     // Skip the metadata payload and the size of the tarball
     let mut sz = [0; 4];
     assert_eq!(f.read(&mut sz).unwrap(), 4);
-    let sz = ((sz[0] as u32) << 0) | ((sz[1] as u32) << 8) | ((sz[2] as u32) << 16)
-        | ((sz[3] as u32) << 24);
-    f.seek(SeekFrom::Current(sz as i64 + 4)).unwrap();
+    let sz = (u32::from(sz[0]) << 0) | (u32::from(sz[1]) << 8) | (u32::from(sz[2]) << 16)
+        | (u32::from(sz[3]) << 24);
+    f.seek(SeekFrom::Current(i64::from(sz) + 4)).unwrap();
 
     // Verify the tarball
     let mut rdr = GzDecoder::new(f);
     assert_eq!(
         rdr.header().unwrap().filename().unwrap(),
-        "foo-0.0.1.crate".as_bytes()
+        b"foo-0.0.1.crate"
     );
     let mut contents = Vec::new();
     rdr.read_to_end(&mut contents).unwrap();
diff --git a/tests/testsuite/required_features.rs b/tests/testsuite/required_features.rs
index 64d6d0c882e..52cc4db4165 100644
--- a/tests/testsuite/required_features.rs
+++ b/tests/testsuite/required_features.rs
@@ -345,20 +345,20 @@ fn test_default_features() {
     assert_that(
         p.cargo("test").arg("--no-default-features"),
         execs()
-            .with_stderr(format!(
+            .with_stderr(
                 "[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]"
-            ))
+            )
             .with_stdout(""),
     );
 
     assert_that(
         p.cargo("test").arg("--test=foo"),
         execs()
-            .with_stderr(format!(
+            .with_stderr(
                 "\
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 [RUNNING] target/debug/deps/foo-[..][EXE]"
-            ))
+            )
             .with_stdout_contains("test test ... ok"),
     );
 
@@ -471,9 +471,9 @@ fn test_multiple_required_features() {
     assert_that(
         p.cargo("test").arg("--no-default-features"),
         execs()
-            .with_stderr(format!(
+            .with_stderr(
                 "[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]"
-            ))
+            )
             .with_stdout(""),
     );
 }
@@ -530,18 +530,18 @@ fn bench_default_features() {
     assert_that(
         p.cargo("bench").arg("--no-default-features"),
         execs()
-            .with_stderr(format!("[FINISHED] release [optimized] target(s) in [..]"))
+            .with_stderr("[FINISHED] release [optimized] target(s) in [..]".to_string())
             .with_stdout(""),
     );
 
     assert_that(
         p.cargo("bench").arg("--bench=foo"),
         execs()
-            .with_stderr(format!(
+            .with_stderr(
                 "\
 [FINISHED] release [optimized] target(s) in [..]
 [RUNNING] target/release/deps/foo-[..][EXE]"
-            ))
+            )
             .with_stdout_contains("test bench ... bench: [..]"),
     );
 
@@ -689,7 +689,7 @@ fn bench_multiple_required_features() {
     assert_that(
         p.cargo("bench").arg("--no-default-features"),
         execs()
-            .with_stderr(format!("[FINISHED] release [optimized] target(s) in [..]"))
+            .with_stderr("[FINISHED] release [optimized] target(s) in [..]")
             .with_stdout(""),
     );
 }
@@ -728,13 +728,13 @@ fn install_default_features() {
 
     assert_that(
         p.cargo("install --path .").arg("--no-default-features"),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 [INSTALLING] foo v0.0.1 ([..])
 [FINISHED] release [optimized] target(s) in [..]
 [ERROR] no binaries are available for install using the selected features
 "
-        )),
+        ),
     );
     assert_that(cargo_home(), is_not(has_installed_exe("foo")));
 
@@ -749,7 +749,7 @@ fn install_default_features() {
         p.cargo("install --path .")
             .arg("--bin=foo")
             .arg("--no-default-features"),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 [INSTALLING] foo v0.0.1 ([..])
 [ERROR] failed to compile `foo v0.0.1 ([..])`, intermediate artifacts can be found at \
@@ -759,7 +759,7 @@ Caused by:
   target `foo` in package `foo` requires the features: `a`
 Consider enabling them by passing e.g. `--features=\"a\"`
 "
-        )),
+        ),
     );
     assert_that(cargo_home(), is_not(has_installed_exe("foo")));
 
@@ -774,7 +774,7 @@ Consider enabling them by passing e.g. `--features=\"a\"`
         p.cargo("install --path .")
             .arg("--example=foo")
             .arg("--no-default-features"),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 [INSTALLING] foo v0.0.1 ([..])
 [ERROR] failed to compile `foo v0.0.1 ([..])`, intermediate artifacts can be found at \
@@ -784,7 +784,7 @@ Caused by:
   target `foo` in package `foo` requires the features: `a`
 Consider enabling them by passing e.g. `--features=\"a\"`
 "
-        )),
+        ),
     );
     assert_that(cargo_home(), is_not(has_installed_exe("foo")));
 }
@@ -1092,9 +1092,9 @@ Consider enabling them by passing e.g. `--features=\"bar/a\"`
     assert_that(
         p.cargo("test"),
         execs()
-            .with_stderr(format!(
+            .with_stderr(
                 "[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]"
-            ))
+            )
             .with_stdout(""),
     );
 
@@ -1119,7 +1119,7 @@ Consider enabling them by passing e.g. `--features=\"bar/a\"`
         assert_that(
             p.cargo("bench"),
             execs()
-                .with_stderr(format!("[FINISHED] release [optimized] target(s) in [..]"))
+                .with_stderr("[FINISHED] release [optimized] target(s) in [..]")
                 .with_stdout(""),
         );
 
@@ -1144,13 +1144,13 @@ Consider enabling them by passing e.g. `--features=\"bar/a\"`
     // install
     assert_that(
         p.cargo("install --path ."),
-        execs().with_status(101).with_stderr(format!(
+        execs().with_status(101).with_stderr(
             "\
 [INSTALLING] foo v0.0.1 ([..])
 [FINISHED] release [optimized] target(s) in [..]
 [ERROR] no binaries are available for install using the selected features
 "
-        )),
+        ),
     );
     assert_that(cargo_home(), is_not(has_installed_exe("foo")));
 
diff --git a/tests/testsuite/rustc.rs b/tests/testsuite/rustc.rs
index cc3f6ff7d8a..20040ca6be0 100644
--- a/tests/testsuite/rustc.rs
+++ b/tests/testsuite/rustc.rs
@@ -1,7 +1,7 @@
 use support::{basic_manifest, basic_bin_manifest, basic_lib_manifest, execs, project};
 use support::hamcrest::assert_that;
 
-const CARGO_RUSTC_ERROR: &'static str =
+const CARGO_RUSTC_ERROR: &str =
     "[ERROR] extra arguments to `rustc` can only be passed to one target, consider filtering
 the package by passing e.g. `--lib` or `--bin NAME` to specify a single target";
 
diff --git a/tests/testsuite/rustflags.rs b/tests/testsuite/rustflags.rs
index 1c81ee21d81..1940f12cf49 100644
--- a/tests/testsuite/rustflags.rs
+++ b/tests/testsuite/rustflags.rs
@@ -678,7 +678,7 @@ fn build_rustflags_normal_source_with_target() {
         )
         .build();
 
-    let ref host = rustc_host();
+    let host = &rustc_host();
 
     // Use RUSTFLAGS to pass an argument that will generate an error
     assert_that(
diff --git a/tests/testsuite/support/git.rs b/tests/testsuite/support/git.rs
index 3edbc10b637..a35f65f3ad9 100644
--- a/tests/testsuite/support/git.rs
+++ b/tests/testsuite/support/git.rs
@@ -130,7 +130,7 @@ pub fn add_submodule<'a>(
     t!(origin.fetch(&[], None, None));
     t!(subrepo.checkout_head(None));
     t!(s.add_finalize());
-    return s;
+    s
 }
 
 pub fn commit(repo: &git2::Repository) -> git2::Oid {
diff --git a/tests/testsuite/support/mod.rs b/tests/testsuite/support/mod.rs
index 602e4f8a9e2..7d64d4a1f5d 100644
--- a/tests/testsuite/support/mod.rs
+++ b/tests/testsuite/support/mod.rs
@@ -351,7 +351,7 @@ impl Project {
     pub fn process<T: AsRef<OsStr>>(&self, program: T) -> ProcessBuilder {
         let mut p = ::support::process(program);
         p.cwd(self.root());
-        return p;
+        p
     }
 
     /// Create a `ProcessBuilder` to run cargo.
@@ -361,7 +361,7 @@ impl Project {
     pub fn cargo(&self, cmd: &str) -> ProcessBuilder {
         let mut p = self.process(&cargo_exe());
         split_and_add_args(&mut p, cmd);
-        return p;
+        p
     }
 
     /// Returns the contents of `Cargo.lock`.
@@ -779,7 +779,7 @@ impl Execs {
                 .map_err(|_| "stdout was not utf8 encoded".to_owned())?;
             let lines = stdout
                 .lines()
-                .filter(|line| line.starts_with("{"))
+                .filter(|line| line.starts_with('{'))
                 .collect::<Vec<_>>();
             if lines.len() != objects.len() {
                 return Err(format!(
@@ -935,7 +935,7 @@ impl Execs {
                         }
                     };
                 }
-                if a.len() > 0 {
+                if !a.is_empty() {
                     Err(format!(
                         "Output included extra lines:\n\
                          {}\n",
@@ -1073,8 +1073,8 @@ fn find_mismatch<'a>(expected: &'a Value, actual: &'a Value) -> Option<(&'a Valu
                 },
             );
 
-            if l.len() > 0 {
-                assert!(r.len() > 0);
+            if !l.is_empty() {
+                assert!(!r.is_empty());
                 Some((&l[0], &r[0]))
             } else {
                 assert_eq!(r.len(), 0);
@@ -1255,8 +1255,8 @@ pub fn basic_lib_manifest(name: &str) -> String {
     )
 }
 
-pub fn path2url(p: PathBuf) -> Url {
-    Url::from_file_path(&*p).ok().unwrap()
+pub fn path2url<P: AsRef<Path>>(p: P) -> Url {
+    Url::from_file_path(p).ok().unwrap()
 }
 
 fn substitute_macros(input: &str) -> String {
@@ -1287,10 +1287,10 @@ fn substitute_macros(input: &str) -> String {
         ("[EXE]", if cfg!(windows) { ".exe" } else { "" }),
     ];
     let mut result = input.to_owned();
-    for &(pat, subst) in macros.iter() {
+    for &(pat, subst) in &macros {
         result = result.replace(pat, subst)
     }
-    return result;
+    result
 }
 
 pub mod install;
@@ -1357,7 +1357,7 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
      .env_remove("GIT_COMMITTER_EMAIL")
      .env_remove("CARGO_TARGET_DIR")     // we assume 'target'
      .env_remove("MSYSTEM"); // assume cmd.exe everywhere on windows
-    return p;
+    p
 }
 
 pub trait ChannelChanger: Sized {
diff --git a/tests/testsuite/support/registry.rs b/tests/testsuite/support/registry.rs
index 4422b10290f..3e07113d872 100644
--- a/tests/testsuite/support/registry.rs
+++ b/tests/testsuite/support/registry.rs
@@ -289,7 +289,7 @@ impl Package {
             ));
         }
 
-        return cksum;
+        cksum
     }
 
     fn make_archive(&self) {
diff --git a/tests/testsuite/tool_paths.rs b/tests/testsuite/tool_paths.rs
index f5710a43a10..ab07d213508 100644
--- a/tests/testsuite/tool_paths.rs
+++ b/tests/testsuite/tool_paths.rs
@@ -124,7 +124,7 @@ fn relative_tools() {
         .build();
 
     let foo_path = p.root().join("bar");
-    let foo_url = path2url(foo_path.clone());
+    let foo_url = path2url(&foo_path);
     let prefix = p.root().into_os_string().into_string().unwrap();
     let output = if cfg!(windows) {
         (