diff --git a/src/error.rs b/src/error.rs
index 349d727..6d13a91 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -180,6 +180,7 @@ pub enum Error {
 /// A specialized `Result` type used by `mlua`'s API.
 pub type Result<T> = StdResult<T, Error>;
 
+#[cfg(not(tarpaulin_include))]
 impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match *self {
diff --git a/src/lua.rs b/src/lua.rs
index d463dfe..9757ce8 100644
--- a/src/lua.rs
+++ b/src/lua.rs
@@ -93,7 +93,7 @@ struct MemoryInfo {
 /// More information can be found in the Lua 5.x [documentation].
 ///
 /// [documentation]: https://www.lua.org/manual/5.4/manual.html#2.5
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum GCMode {
     Incremental,
     /// Requires `feature = "lua54"`
@@ -525,6 +525,7 @@ impl Lua {
     // Executes module entrypoint function, which returns only one Value.
     // The returned value then pushed to the Lua stack.
     #[doc(hidden)]
+    #[cfg(not(tarpaulin_include))]
     pub fn entrypoint1<'lua, 'callback, R, F>(&'lua self, func: F) -> Result<c_int>
     where
         'lua: 'callback,
diff --git a/tests/conversion.rs b/tests/conversion.rs
index 71d76ba..68724f2 100644
--- a/tests/conversion.rs
+++ b/tests/conversion.rs
@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
-use std::ffi::CString;
+use std::ffi::{CStr, CString};
 
 use maplit::{btreemap, btreeset, hashmap, hashset};
 use mlua::{Lua, Result};
@@ -72,7 +72,12 @@ fn test_conv_cstring() -> Result<()> {
     let s = CString::new(b"hello".to_vec()).unwrap();
     lua.globals().set("s", s.clone())?;
     let s2: CString = lua.globals().get("s")?;
-    assert!(s == s2);
+    assert_eq!(s, s2);
+
+    let cs = CStr::from_bytes_with_nul(b"hello\0").unwrap();
+    lua.globals().set("cs", cs)?;
+    let cs2: CString = lua.globals().get("cs")?;
+    assert_eq!(cs, cs2.as_c_str());
 
     Ok(())
 }
diff --git a/tests/memory.rs b/tests/memory.rs
index aa0a809..d17bd66 100644
--- a/tests/memory.rs
+++ b/tests/memory.rs
@@ -1,6 +1,6 @@
 use std::sync::Arc;
 
-use mlua::{Lua, Result, UserData};
+use mlua::{GCMode, Lua, Result, UserData};
 
 #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 use mlua::Error;
@@ -38,6 +38,9 @@ fn test_gc_control() -> Result<()> {
     let lua = Lua::new();
     let globals = lua.globals();
 
+    #[cfg(feature = "lua54")]
+    assert_eq!(lua.gc_gen(0, 0), GCMode::Incremental);
+
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     {
         assert!(lua.gc_is_running());
@@ -59,6 +62,9 @@ fn test_gc_control() -> Result<()> {
     lua.gc_collect()?;
     assert_eq!(Arc::strong_count(&rc), 1);
 
+    #[cfg(feature = "lua54")]
+    assert_eq!(lua.gc_inc(0, 0, 0), GCMode::Generational);
+
     Ok(())
 }
 
diff --git a/tests/thread.rs b/tests/thread.rs
index ebb68a9..995b65f 100644
--- a/tests/thread.rs
+++ b/tests/thread.rs
@@ -93,8 +93,8 @@ fn test_thread() -> Result<()> {
     Ok(())
 }
 
-#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored")))]
 #[test]
+#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored")))]
 fn test_thread_reset() -> Result<()> {
     use mlua::{AnyUserData, UserData};
     use std::sync::Arc;
diff --git a/tests/userdata.rs b/tests/userdata.rs
index e88e97b..1139c6a 100644
--- a/tests/userdata.rs
+++ b/tests/userdata.rs
@@ -362,6 +362,12 @@ fn test_fields() -> Result<()> {
                 index.set("f", 321)?;
                 Ok(index)
             });
+            fields.add_meta_field_with(MetaMethod::NewIndex, |lua| {
+                lua.create_function(|lua, (_, field, val): (AnyUserData, String, Value)| {
+                    lua.globals().set(field, val)?;
+                    Ok(())
+                })
+            })
         }
     }
 
@@ -379,6 +385,9 @@ fn test_fields() -> Result<()> {
         assert(ud.uval == "hello")
 
         assert(ud.f == 321)
+
+        ud.unknown = 789
+        assert(unknown == 789)
     "#,
     )
     .exec()?;