Use colors inside the test

src/exercise.rs

@@ -69,7 +69,17 @@ impl Exercise {
     pub fn run(&self) -> Result<Output> {
         match self.mode {
             Mode::Run => self.cargo_cmd("run", &[]),
-            Mode::Test => self.cargo_cmd("test", &["--", "--nocapture", "--format", "pretty"]),
+            Mode::Test => self.cargo_cmd(
+                "test",
+                &[
+                    "--",
+                    "--color",
+                    "always",
+                    "--nocapture",
+                    "--format",
+                    "pretty",
+                ],
+            ),
             Mode::Clippy => self.cargo_cmd(
                 "clippy",
                 &["--", "-D", "warnings", "-D", "clippy::float_cmp"],