bufferpool-specific "unit" tests

tests/bufferpool_tests.rs

@@ -0,0 +1,45 @@
+extern crate cowabunga_rs;
+use cowabunga_rs::bufferpool::*;
+use cowabunga_rs::constants::*;
+
+/// Simplest conceivable write_next_value() use
+#[test]
+fn test_simple_write_next_value()  -> Result<(), String> {
+    let mut bp = BufferPool::new();
+
+    let ppid = bp.allocate_page("test_tbl".to_string(), 0);
+
+    let offset = bp.write_next_value(ppid, Some(42))?;
+    let val_read = bp.read(ppid, offset);
+
+    assert_eq!(val_read, 42);
+    Ok(())
+}
+
+
+/// Force an eviction to occur using allocate, reads and writes
+#[test]
+fn test_full_bufferpool()  -> Result<(), String> {
+    let mut bp = BufferPool::new();
+
+    let mut ppids: Vec<PhysicalPageID> = Vec::new();
+
+    // create more pages than frames (all in one column)
+    for _ in (1..=BP_NUM_FRAMES+1) {
+        ppids.push(bp.allocate_page("test_tbl".to_string(), 0));
+    }
+
+    for (i, ppid) in ppids.iter().enumerate() {
+        bp.write_next_value(*ppid, Some(i as i64 + 1));
+    }
+
+    let expected_values: Vec<i64> = (1..=BP_NUM_FRAMES+1).collect();
+    let mut observed_values: Vec<i64> = Vec::new();
+
+    for ppid in &ppids {
+        observed_values.push(bp.read(*ppid, 0)?);
+    }
+
+    assert_eq!(expected_values, observed_values);
+    Ok(())
+}