du: Fix incorrect block size assumption.

du and other tools like stat assume a 512 byte block. ls is the only
tool to use 1024.

Add Simple set of tests

tests/fixtures/du/subdir/subwords2.txt

@@ -0,0 +1 @@
+hello

tests/fixtures/du/words.txt

@@ -0,0 +1 @@
+hello

tests/test_du.rs

@@ -0,0 +1,62 @@
+use common::util::*;
+use std::fs::set_permissions;
+
+static SUB_DIR: &str = "subdir";
+static SUB_FILE: &str = "subdir/subwords.txt";
+static SUB_LINK: &str = "subdir/sublink.txt";
+
+#[test]
+fn test_du_basics() {
+    let (_at, mut ucmd) = at_and_ucmd!();
+
+    let result = ucmd.run();
+    assert!(result.success);
+    assert_eq!(result.stderr, "");
+    assert_eq!(result.stdout, "24\t./subdir\n32\t./\n");
+}
+
+#[test]
+fn test_du_basics_subdir() {
+    let (_at, mut ucmd) = at_and_ucmd!();
+
+    let result = ucmd.arg(SUB_DIR).run();
+    assert!(result.success);
+    assert_eq!(result.stderr, "");
+    assert_eq!(result.stdout, "24\tsubdir\n");
+}
+
+#[test]
+fn test_du_basics_bad_name() {
+    let (_at, mut ucmd) = at_and_ucmd!();
+
+    let result = ucmd.arg("bad_name").run();
+    assert_eq!(result.stdout, "");
+    assert_eq!(result.stderr, "du: bad_name: No such file or directory\n");
+}
+
+#[test]
+fn test_du_soft_link() {
+    let ts = TestScenario::new("du");
+
+    let link = ts.cmd("ln").arg("-s").arg(SUB_FILE).arg(SUB_LINK).run();
+    assert!(link.success);
+
+    let result = ts.ucmd().arg(SUB_DIR).run();
+    assert!(result.success);
+    assert_eq!(result.stderr, "");
+    assert_eq!(result.stdout, "32\tsubdir\n");
+}
+
+// todo:
+// du on file with no permissions
+// du on soft link
+// du on hard link
+// du on multi dir with '-d'
+//
+/*
+ * let mut permissions = at.make_file(TEST_HELLO_WORLD_DEST)
+ * .metadata()
+ * .unwrap()
+ * .permissions();
+ * permissions.set_readonly(true);
+ */

tests/tests.rs

@@ -52,6 +52,7 @@ generic! {
     "cut", test_cut;
     "dircolors", test_dircolors;
     "dirname", test_dirname;
+    "du", test_du;
     "echo", test_echo;
     "env", test_env;
     "expr", test_expr;