Update readme

README.md

@@ -11,7 +11,6 @@ This crate exports multiple macros for snapshot testing:
 
 - `assert_snapshot_matches!` for comparing basic string snapshots.
 - `assert_debug_snapshot_matches!` for comparing `Debug` outputs of values.
-- `assert_display_snapshot_matches!` for comparing `Display` outputs of values.
 - `assert_yaml_snapshot_matches!` for comparing YAML serialized
   output of types implementing `serde::Serialize`.
 - `assert_ron_snapshot_matches!` for comparing RON serialized output of
@@ -21,7 +20,8 @@ This crate exports multiple macros for snapshot testing:
 
 Snapshots are stored in the `snapshots` folder right next to the test file
 where this is used.  The name of the file is `<module>__<name>.snap` where
-the `name` of the snapshot has to be provided to the assertion macro.
+the `name` of the snapshot has to be provided to the assertion macro.  If
+no name is provided the name is derived from the test name.
 
 Additionally snapshots can also be stored inline.  In that case the
 `cargo-insta` tool is necessary.  See [inline snapshots](#inline-snapshots)
@@ -62,6 +62,9 @@ fn test_snapshots() {
 }
 ```
 
+(If you do not want to provide a name for the snapshot read about
+[unnamed snapshots](#unnamed-snapshots).)
+
 The recommended flow is to run the tests once, have them fail and check
 if the result is okay.  By default the new snapshots are stored next
 to the old ones with the extra `.new` extension.  Once you are satisifed
@@ -188,6 +191,29 @@ assert_yaml_snapshot_matches!("user", &User {
 });
 ```
 
+## Unnamed Snapshots
+
+All snapshot assertion functions let you leave out the snapshot name.  In
+that case the snapshot name is derived from the test name.  This works
+because the rust test runner names the thread by the test name and the
+name is taken from the thread name.  In case your test spawns additional
+threads this will not work and you will need to provide a name explicitly.
+
+Additionally if you have multiple snapshot assertions per test name a
+counter will be appended:
+
+```rust
+#[test]
+fn test_something() {
+    assert_snapshot_matches!("first value");
+    assert_snapshot_matches!("second value");
+}
+```
+
+This will create two snapshots: `something` for the first value and
+`something-2` for the second value.  The leading `test_` prefix is removed
+if the function starts with that name.
+
 ## Inline Snapshots
 
 Additionally snapshots can also be stored inline.  In that case the format