test: add unit test for create_caster_fn_ident

5 files changed, 113 insertions, 6 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 088bc01..9bf4a0a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -60,6 +60,7 @@ tokio = { version = "1.20.1", features = ["macros", "rt-multi-thread", "time"] }
 [workspace]
 members = [
 	"macros",
-	"examples/with-3rd-party/third-party-lib"
+	"test_util_macros",
+	"examples/with-3rd-party/third-party-lib",
 ]
 
diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index a2ed87b..2434028 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -33,3 +33,4 @@ syrette = { version = "0.4.1", path = ".." }
 mockall = "0.11.1"
 pretty_assertions = "1.3.0"
 syn = { version = "1.0.96", features = ["full", "extra-traits"] }
+test_util_macros = { path = "../test_util_macros" }
diff --git a/macros/src/libs/intertrait_macros/gen_caster.rs b/macros/src/libs/intertrait_macros/gen_caster.rs
index a76bb52..c2fa226 100644
--- a/macros/src/libs/intertrait_macros/gen_caster.rs
+++ b/macros/src/libs/intertrait_macros/gen_caster.rs
@@ -28,7 +28,7 @@ pub fn generate_caster(
     sync: bool,
 ) -> TokenStream
 {
-    let fn_ident = create_caster_fn_ident();
+    let fn_ident = create_caster_fn_ident(Uuid::new_v4());
 
     let new_caster = if sync {
         quote! {
@@ -86,18 +86,65 @@ pub fn generate_caster(
     }
 }
 
-fn create_caster_fn_ident() -> Ident
+fn create_caster_fn_ident(uuid: impl IUuid) -> Ident
 {
     let buf = &mut [0u8; FN_BUF_LEN];
 
     buf[..CASTER_FN_NAME_PREFIX.len()].copy_from_slice(CASTER_FN_NAME_PREFIX);
 
-    Uuid::new_v4()
-        .to_simple()
-        .encode_lower(&mut buf[CASTER_FN_NAME_PREFIX.len()..]);
+    uuid.encode_simple_lower_into(&mut buf[CASTER_FN_NAME_PREFIX.len()..]);
 
     let fn_name =
         from_utf8(&buf[..FN_BUF_LEN]).expect("Created caster function name is not UTF-8");
 
     format_ident!("{}", fn_name)
 }
+
+/// Simple interface for `Uuid`.
+///
+/// Created for ease of testing the [`create_caster_fn_ident`] function.
+///
+/// [`Uuid`]: uuid::Uuid
+#[cfg_attr(test, mockall::automock)]
+trait IUuid
+{
+    /// Writes the Uuid as a simple lower-case string to `buf`.
+    fn encode_simple_lower_into(self, buf: &mut [u8]);
+}
+
+impl IUuid for Uuid
+{
+    fn encode_simple_lower_into(self, buf: &mut [u8])
+    {
+        self.to_simple().encode_lower(buf);
+    }
+}
+
+#[cfg(test)]
+mod tests
+{
+    use pretty_assertions::assert_eq;
+    use test_util_macros::repeat_char;
+
+    use super::*;
+
+    #[test]
+    fn can_create_caster_fn_ident()
+    {
+        let mut uuid_mock = MockIUuid::new();
+
+        uuid_mock
+            .expect_encode_simple_lower_into()
+            .return_once(|buf| {
+                for index in 0..(FN_BUF_LEN - 2) {
+                    buf[index] = b'f';
+                }
+            })
+            .once();
+
+        assert_eq!(
+            create_caster_fn_ident(uuid_mock),
+            format_ident!(concat!("__", repeat_char!('f', 32)))
+        );
+    }
+}
diff --git a/test_util_macros/Cargo.toml b/test_util_macros/Cargo.toml
new file mode 100644
index 0000000..8848961
--- /dev/null
+++ b/test_util_macros/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "test_util_macros"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc_macro = true
+
+[dependencies]
+syn = { version = "1.0.96", features = ["full"] }
+quote = "1.0.18"
diff --git a/test_util_macros/src/lib.rs b/test_util_macros/src/lib.rs
new file mode 100644
index 0000000..aa87ecf
--- /dev/null
+++ b/test_util_macros/src/lib.rs
@@ -0,0 +1,47 @@
+#![deny(clippy::all)]
+#![deny(clippy::pedantic)]
+#![deny(missing_docs)]
+
+//! Internal macros used by tests.
+
+use std::iter::repeat;
+
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::parse::Parse;
+use syn::{parse_macro_input, LitChar, LitInt, Token};
+
+/// Repeats a character N number of times.
+#[proc_macro]
+pub fn repeat_char(input: TokenStream) -> TokenStream
+{
+    let RepeatMacroArgs { character, count } =
+        parse_macro_input!(input as RepeatMacroArgs);
+
+    let repeated = repeat(character.value()).take(count).collect::<String>();
+
+    quote! {
+        #repeated
+    }
+    .into()
+}
+
+struct RepeatMacroArgs
+{
+    character: LitChar,
+    count: usize,
+}
+
+impl Parse for RepeatMacroArgs
+{
+    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self>
+    {
+        let character = input.parse::<LitChar>()?;
+
+        input.parse::<Token![,]>()?;
+
+        let count = input.parse::<LitInt>()?.base10_parse::<usize>()?;
+
+        Ok(Self { character, count })
+    }
+}