Add initial test for tsort.

Makefile

@@ -179,6 +179,7 @@ TEST_PROGS  := \
   tr \
   true \
   truncate \
+  tsort \
   unexpand
 
 TEST        ?= $(TEST_PROGS)

test/fixtures/tsort/call_graph.expected

@@ -0,0 +1,17 @@
+main
+parse_options
+tail_file
+tail_forever
+tail
+recheck
+write_header
+tail_lines
+tail_bytes
+pretty_name
+start_lines
+file_lines
+pipe_lines
+xlseek
+start_bytes
+pipe_bytes
+dump_remainder

test/fixtures/tsort/call_graph.txt

@@ -0,0 +1,22 @@
+main parse_options
+main tail_file
+main tail_forever
+tail_file pretty_name
+tail_file write_header
+tail_file tail
+tail_forever recheck
+tail_forever pretty_name
+tail_forever write_header
+tail_forever dump_remainder
+tail tail_lines
+tail tail_bytes
+tail_lines start_lines
+tail_lines dump_remainder
+tail_lines file_lines
+tail_lines pipe_lines
+tail_bytes xlseek
+tail_bytes start_bytes
+tail_bytes dump_remainder
+tail_bytes pipe_bytes
+file_lines dump_remainder
+recheck pretty_name

test/tsort.rs

@@ -0,0 +1,26 @@
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
+use std::process::Command;
+
+static PROGNAME: &'static str = "./tsort";
+
+fn get_file_contents(name: &str) -> Vec<u8> {
+    let mut f = File::open(Path::new(name)).unwrap();
+    let mut contents: Vec<u8> = vec!();
+    let _ = f.read_to_end(&mut contents);
+    contents
+}
+
+#[test]
+fn test_sort_call_graph() {
+    let input = "call_graph.txt";
+    let output = "call_graph.expected";
+
+    let po = Command::new(PROGNAME)
+        .arg(input)
+        .output()
+        .unwrap_or_else(|err| panic!("{}", err));
+
+    assert_eq!(String::from_utf8(po.stdout).unwrap(), String::from_utf8(get_file_contents(output)).unwrap());
+}