added forgotten tests

tests/char.rs

@@ -0,0 +1,44 @@
+use std::convert::TryFrom;
+use std::ops::RangeBounds;
+
+fn test_char_coverage<R>(n: usize, range: R)
+where
+    R: Iterator<Item = char> + RangeBounds<char> + Clone,
+{
+    use std::collections::HashSet;
+
+    let all: HashSet<char> = range.clone().collect();
+    let mut covered = HashSet::new();
+    for _ in 0..n {
+        let c = fastrand::char(range.clone());
+        assert!(all.contains(&c));
+        covered.insert(c);
+    }
+    assert_eq!(covered, all);
+}
+
+#[test]
+fn test_char() {
+    // ASCII control chars.
+    let nul = 0u8 as char;
+    let soh = 1u8 as char;
+    let stx = 2u8 as char;
+    // Some undefined Hangul Jamo codepoints just before
+    // the surrogate area.
+    let last_jamo = char::try_from(0xd7ffu32).unwrap();
+    let penultimate_jamo = char::try_from(last_jamo as u32 - 1).unwrap();
+    // Private-use codepoints just after the surrogate area.
+    let first_private = char::try_from(0xe000u32).unwrap();
+    let second_private = char::try_from(first_private as u32 + 1).unwrap();
+    // Private-use codepoints at the end of Unicode space.
+    let last_private = std::char::MAX;
+    let penultimate_private = char::try_from(last_private as u32 - 1).unwrap();
+
+    test_char_coverage(100, nul..stx);
+    test_char_coverage(100, nul..=soh);
+
+    test_char_coverage(400, penultimate_jamo..second_private);
+    test_char_coverage(400, penultimate_jamo..=second_private);
+
+    test_char_coverage(100, penultimate_private..=last_private);
+}