feat: add singularity module (#932)

tests/testsuite/main.rs

@@ -18,6 +18,7 @@ mod line_break;
 mod modules;
 mod nix_shell;
 mod python;
+mod singularity;
 mod terraform;
 mod time;
 mod username;

tests/testsuite/singularity.rs

@@ -0,0 +1,18 @@
+use ansi_term::Color;
+use std::io;
+
+use crate::common;
+
+#[test]
+fn env_set() -> io::Result<()> {
+    let output = common::render_module("singularity")
+        .env_clear()
+        .env("SINGULARITY_NAME", "centos.img")
+        .output()?;
+
+    let expected = format!("{} ", Color::Blue.bold().dimmed().paint("[centos.img]"));
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    assert_eq!(expected, actual);
+    Ok(())
+}