Wrote tests for compressor functions (#48)

* Wrote tests for create_new_tree

* wrote tests for get_delta

src/compressor/level_tests.rs

@@ -0,0 +1,80 @@
+use crate::compressor::Level;
+
+#[test]
+fn new_produces_empty_level() {
+    let l = Level::new(15);
+    assert_eq!(l.max_length, 15);
+    assert_eq!(l.current_chain_length, 0);
+    assert_eq!(l.current, None);
+}
+
+#[test]
+fn update_adds_to_non_full_level() {
+    let mut l = Level::new(10);
+    l.update(7, true);
+    assert_eq!(l.max_length, 10);
+    assert_eq!(l.current_chain_length, 1);
+    assert_eq!(l.current, Some(7));
+}
+
+#[test]
+#[should_panic(expected = "Tried to add to an already full level")]
+fn update_panics_if_adding_and_too_full() {
+    let mut l = Level::new(5);
+    l.update(1, true);
+    l.update(2, true);
+    l.update(3, true);
+    l.update(4, true);
+    l.update(5, true);
+    l.update(6, true);
+}
+
+#[test]
+fn update_resets_level_correctly() {
+    let mut l = Level::new(5);
+    l.update(1, true);
+    l.update(2, true);
+    l.update(3, true);
+    l.update(4, true);
+    l.update(5, true);
+    l.update(6, false);
+    assert_eq!(l.max_length, 5);
+    assert_eq!(l.current_chain_length, 1);
+    assert_eq!(l.current, Some(6));
+}
+
+#[test]
+fn get_current_returns_current() {
+    let mut l = Level::new(5);
+    assert_eq!(l.get_current(), None);
+    l.update(23, true);
+    assert_eq!(l.get_current(), Some(23));
+}
+
+#[test]
+fn has_space_returns_true_if_empty() {
+    let l = Level::new(15);
+    assert_eq!(l.has_space(), true);
+}
+
+#[test]
+fn has_space_returns_true_if_part_full() {
+    let mut l = Level::new(15);
+    l.update(12, true);
+    l.update(234, true);
+    l.update(1, true);
+    l.update(143, true);
+    l.update(15, true);
+    assert_eq!(l.has_space(), true);
+}
+
+#[test]
+fn has_space_returns_false_if_full() {
+    let mut l = Level::new(5);
+    l.update(1, true);
+    l.update(2, true);
+    l.update(3, true);
+    l.update(4, true);
+    l.update(5, true);
+    assert_eq!(l.has_space(), false);
+}