feat: Implement the prompt module for time (#138)

Add a module which displays the current time in a format requested by
the user. Disabled by default.

tests/testsuite/main.rs

@@ -15,4 +15,5 @@ mod nix_shell;
 mod nodejs;
 mod python;
 mod ruby;
+mod time;
 mod username;

tests/testsuite/time.rs

@@ -0,0 +1,62 @@
+use ansi_term::Color;
+use std::fs;
+use std::io;
+use std::path::Path;
+use tempfile::TempDir;
+
+use crate::common::{self, TestCommand};
+
+/* Note: tests in this crate cannot rely on the actual time displayed by
+the module, since that is dependent on the time inside the test environment,
+which we cannot control.
+
+However, we *can* test certain things here, such as the fact that the module
+should not display when disabled, should display *something* when enabled,
+and should have the correct prefixes and suffixes in a given config */
+
+#[test]
+fn config_enabled() -> io::Result<()> {
+    let output = common::render_module("time")
+        .use_config(toml::toml! {
+            [time]
+            disabled = false
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    // We can't test what it actually is...but we can assert it's not blank
+    assert!(!actual.is_empty());
+    Ok(())
+}
+
+#[test]
+fn config_blank() -> io::Result<()> {
+    let output = common::render_module("time").output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    let expected = "";
+    assert_eq!(expected, actual);
+    Ok(())
+}
+
+#[test]
+fn config_check_prefix_and_suffix() -> io::Result<()> {
+    let output = common::render_module("time")
+        .use_config(toml::toml! {
+            [time]
+            disabled = false
+            format = "[%T]"
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    // This is the prefix with "at ", the color code, then the prefix char [
+    let col_prefix = format!("at {}{}[", '\u{1b}', "[1;33m");
+
+    // This is the suffix with suffix char ']', then color codes, then a space
+    let col_suffix = format!("]{}{} ", '\u{1b}', "[0m");
+
+    assert!(actual.starts_with(&col_prefix));
+    assert!(actual.ends_with(&col_suffix));
+    Ok(())
+}