Add snapshot testing

tests/tests.rs

@@ -0,0 +1,33 @@
+mod tester;
+
+use tester::BatTester;
+
+static STYLES: &'static [&'static str] = &[
+    "changes",
+    "grid",
+    "header",
+    "numbers",
+    "changes,grid",
+    "changes,header",
+    "changes,numbers",
+    "grid,header",
+    "grid,numbers",
+    "header,numbers",
+    "changes,grid,header",
+    "changes,grid,numbers",
+    "changes,header,numbers",
+    "grid,header,numbers",
+    "changes,grid,header,numbers",
+    "full",
+    "plain",
+];
+
+#[test]
+fn test_snapshots() {
+    let bat_tester = BatTester::new();
+
+    for style in STYLES {
+        println!("testing {}", style);
+        bat_tester.test_snapshot(&*style);
+    }
+}