3 files changed, 67 insertions, 0 deletions
diff --git a/src/insn.rs b/src/insn.rs
index db62e6c..2a6ca42 100644
--- a/src/insn.rs
+++ b/src/insn.rs
@@ -6,6 +6,7 @@ mod jmp;
 mod jnz;
 mod jz;
 mod mov;
+mod nop;
 mod ret;
 mod test;
 
diff --git a/src/insn/nop.rs b/src/insn/nop.rs
new file mode 100644
index 0000000..82057db
--- /dev/null
+++ b/src/insn/nop.rs
@@ -0,0 +1,7 @@
+use crate::Asm;
+
+impl Asm {
+    pub fn nop(&mut self) {
+        self.emit(&[0x90]);
+    }
+}
diff --git a/tests/jmp.rs b/tests/jmp.rs
new file mode 100644
index 0000000..2524218
--- /dev/null
+++ b/tests/jmp.rs
@@ -0,0 +1,59 @@
+use juicebox_asm::prelude::*;
+
+#[test]
+#[should_panic]
+fn unbound_label() {
+    let _l = Label::new();
+}
+
+#[test]
+#[should_panic]
+fn unbound_label2() {
+    let mut lbl = Label::new();
+    let mut asm = Asm::new();
+    asm.jmp(&mut lbl);
+}
+
+#[test]
+fn jmp_label() {
+    {
+        // Bind first.
+        let mut lbl = Label::new();
+        let mut asm = Asm::new();
+        asm.bind(&mut lbl);
+        asm.jmp(&mut lbl);
+        // 0xfffffffb -> -5
+        assert_eq!(asm.into_code(), [0xe9, 0xfb, 0xff, 0xff, 0xff]);
+    }
+    {
+        // Bind later.
+        let mut lbl = Label::new();
+        let mut asm = Asm::new();
+        asm.jmp(&mut lbl);
+        asm.bind(&mut lbl);
+        assert_eq!(asm.into_code(), [0xe9, 0x00, 0x00, 0x00, 0x00]);
+    }
+}
+
+#[test]
+fn jmp_label2() {
+    {
+        let mut lbl = Label::new();
+        let mut asm = Asm::new();
+        asm.jmp(&mut lbl);
+        asm.nop();
+        asm.nop();
+        asm.bind(&mut lbl);
+        assert_eq!(asm.into_code(), [0xe9, 0x02, 0x00, 0x00, 0x00, 0x90, 0x90]);
+    }
+    {
+        let mut lbl = Label::new();
+        let mut asm = Asm::new();
+        asm.jmp(&mut lbl);
+        for _ in 0..0x1ff {
+            asm.nop();
+        }
+        asm.bind(&mut lbl);
+        assert_eq!(asm.into_code()[..5], [0xe9, 0xff, 0x01, 0x00, 0x00]);
+    }
+}