diff --git a/tests/ui/panic-handler-argument.rs b/tests/ui/panic-handler-argument.rs
new file mode 100644
index 00000000..e664ab00
--- /dev/null
+++ b/tests/ui/panic-handler-argument.rs
@@ -0,0 +1,5 @@
+#![no_main]
+#![no_std]
+
+#[defmt::panic_handler]
+fn foo(x: bool) -> ! { info!("{:?}", x); loop {} }
diff --git a/tests/ui/panic-handler-argument.stderr b/tests/ui/panic-handler-argument.stderr
new file mode 100644
index 00000000..b40d97d4
--- /dev/null
+++ b/tests/ui/panic-handler-argument.stderr
@@ -0,0 +1,5 @@
+error: function must have signature `fn() -> !`
+ --> $DIR/panic-handler-argument.rs:5:4
+  |
+5 | fn foo(x: bool) -> ! { info!("{:?}", x); loop {} }
+  |    ^^^
diff --git a/tests/ui/panic-handler-empty.rs b/tests/ui/panic-handler-empty.rs
new file mode 100644
index 00000000..fa451071
--- /dev/null
+++ b/tests/ui/panic-handler-empty.rs
@@ -0,0 +1,5 @@
+#![no_main]
+#![no_std]
+
+#[defmt::panic_handler]
+fn foo() {}
diff --git a/tests/ui/panic-handler-empty.stderr b/tests/ui/panic-handler-empty.stderr
new file mode 100644
index 00000000..5f05cc9a
--- /dev/null
+++ b/tests/ui/panic-handler-empty.stderr
@@ -0,0 +1,5 @@
+error: function must have signature `fn() -> !`
+ --> $DIR/panic-handler-empty.rs:5:4
+  |
+5 | fn foo() {}
+  |    ^^^
diff --git a/tests/ui/timestamp-input-parameter.rs b/tests/ui/timestamp-input-parameter.rs
new file mode 100644
index 00000000..eb3a3c9b
--- /dev/null
+++ b/tests/ui/timestamp-input-parameter.rs
@@ -0,0 +1,3 @@
+#![no_main]
+#[defmt::timestamp]
+fn foo(x: u64) -> u64 { x + 1 }
diff --git a/tests/ui/timestamp-input-parameter.stderr b/tests/ui/timestamp-input-parameter.stderr
new file mode 100644
index 00000000..b82df7bd
--- /dev/null
+++ b/tests/ui/timestamp-input-parameter.stderr
@@ -0,0 +1,5 @@
+error: function must have signature `fn() -> u64`
+ --> $DIR/timestamp-input-parameter.rs:3:4
+  |
+3 | fn foo(x: u64) -> u64 { x + 1 }
+  |    ^^^