Use macro per-test-file

Signed-off-by: Marcel Müller <neikos@neikos.email>

tests/cases/literals.1-parsed.snap

@@ -0,0 +1,26 @@
+---
+source: tests/file_tests.rs
+expression: parsed
+info:
+  input: "{{ if true }}\n    Hello World!\n{{ end }}"
+  context: {}
+---
+ParsedTemplate {
+    tokens: [
+        [LeftDelim]"{{" (0..2),
+        [Whitespace]" " (2..3),
+        [ConditionalIf]"if" (3..5),
+        [Whitespace]" " (5..6),
+        [Literal(Bool(true))]"true" (6..10),
+        [Whitespace]" " (10..11),
+        [RightDelim]"}}" (11..13),
+        [Whitespace]"\n    " (13..18),
+        [Content]"Hello World!" (18..30),
+        [Whitespace]"\n" (30..31),
+        [LeftDelim]"{{" (31..33),
+        [Whitespace]" " (33..34),
+        [End]"end" (34..37),
+        [Whitespace]" " (37..38),
+        [RightDelim]"}}" (38..40),
+    ],
+}