diff --git a/src/emu.rs b/src/emu.rs
index 39dcae9..c20f5bd 100644
--- a/src/emu.rs
+++ b/src/emu.rs
@@ -1,4 +1,4 @@
-use crate::inst::{AmoOp, Inst, InstCode, IsCompressed};
+use crate::inst::{AmoOp, DecodeError, Inst, IsCompressed};
 use std::{
     fmt::{Debug, Display},
     io::Write,
@@ -66,7 +66,7 @@ impl Memory {
 #[derive(Debug)]
 pub enum Status {
     Trap(&'static str),
-    IllegalInstruction(InstCode, &'static str),
+    IllegalInstruction(DecodeError),
     InvalidMemoryAccess(u32),
     UnalignedPc(u32),
     UnaligneMemoryAccess { addr: u32, required_align: u32 },
@@ -74,6 +74,12 @@ pub enum Status {
     Exit { code: i32 },
 }
 
+impl From<DecodeError> for Status {
+    fn from(value: DecodeError) -> Self {
+        Status::IllegalInstruction(value)
+    }
+}
+
 pub struct Emulator {
     pub mem: Memory,
     pub xreg: [u32; 32],
@@ -87,6 +93,7 @@ pub struct Emulator {
     pub is_breaking: bool,
 
     pub debug: bool,
+    pub break_pc: u32,
     pub ecall_handler: Box<dyn FnMut(&mut Memory, &mut [u32; 32]) -> Result<(), Status>>,
 }
 
@@ -219,7 +226,6 @@ impl Emulator {
         // TODO: add some auxv for the poor process.
         self.mem.store_u32(next_word(), 0)?;
 
-
         Ok(())
     }
 
@@ -238,16 +244,16 @@ impl Emulator {
 
     fn step(&mut self) -> Result<(), Status> {
         let code = self.mem.load_u32(self.pc)?;
-        let (inst, was_compressed) = Inst::decode(code)?;
 
-        if self.is_breaking {
-            self.debug_interactive();
+        if self.debug {
+            print!("0x{:x} ", self.pc);
         }
 
+        let (inst, was_compressed) = Inst::decode(code)?;
+
         if self.debug {
             println!(
-                "0x{:x} {} (sp: {}) {inst:?}",
-                self.pc,
+                "{} (sp: {}) {inst:?}",
                 match was_compressed {
                     IsCompressed::Yes => "C",
                     IsCompressed::No => " ",
@@ -256,6 +262,14 @@ impl Emulator {
             );
         }
 
+        if self.pc == self.break_pc {
+            self.is_breaking = true;
+        }
+
+        if self.is_breaking {
+            self.debug_interactive();
+        }
+
         let next_pc = self.pc.wrapping_add(match was_compressed {
             IsCompressed::Yes => 2,
             IsCompressed::No => 4,
@@ -515,8 +529,8 @@ impl Emulator {
             std::io::stdout().flush().unwrap();
             let mut input = String::new();
             std::io::stdin().read_line(&mut input).unwrap();
-            let input = input.trim();
-            match input {
+            let mut input = input.trim().split_whitespace();
+            match input.next().unwrap_or_default() {
                 "c" => {
                     self.is_breaking = false;
                     return;
@@ -525,7 +539,43 @@ impl Emulator {
                     return;
                 }
                 "q" => std::process::exit(0),
-                "p" => {
+                "m" => {
+                    let Some(size) = input.next() else {
+                        eprintln!("require b/h/w argument for m command");
+                        continue;
+                    };
+                    let Some(addr) = input.next() else {
+                        eprintln!("require address argument for m command");
+                        continue;
+                    };
+                    let Ok(addr) = (if let Some(addr) = addr.strip_prefix("0x") {
+                        u32::from_str_radix(addr, 16)
+                    } else {
+                        u32::from_str_radix(&addr, 10)
+                    }) else {
+                        eprintln!("invalid address");
+                        continue;
+                    };
+                    let value = match size {
+                        "w" => self.mem.load_u32(addr),
+                        "h" => self.mem.load_u16(addr).map(Into::into),
+                        "b" => self.mem.load_u8(addr).map(Into::into),
+                        _ => {
+                            eprintln!("require b/h/w argument for m command");
+                            continue;
+                        }
+                    };
+                    let value = match value {
+                        Ok(v) => v,
+                        Err(e) => {
+                            eprintln!("failed to load value: {e:?}");
+                            continue;
+                        }
+                    };
+
+                    println!("{value} (0x{value:x})");
+                }
+                "r" => {
                     let format_value = |v: u32| {
                         if v == 0 {
                             format!("{:0>8x}", v.black())
@@ -626,7 +676,8 @@ impl Emulator {
                 _ => println!(
                     "commands:
 - ?: help
-- p: print registers
+- r: print registers
+- m <b|h|w> <addr>: read a byte/half/word of memory at an address
 - c: continue until next breakpoint
 - s: step one instruction
 - q: quit"
diff --git a/src/inst.rs b/src/inst.rs
index f57322b..23ab9f9 100644
--- a/src/inst.rs
+++ b/src/inst.rs
@@ -1,4 +1,4 @@
-use crate::emu::{Reg, Status};
+use crate::emu::Reg;
 use std::fmt::{Debug, Display};
 use std::ops::RangeInclusive;
 
@@ -173,6 +173,11 @@ pub enum AmoOp {
     Maxu,
 }
 
+pub struct DecodeError {
+    pub instruction: u32,
+    pub unexpected_field: &'static str,
+}
+
 impl Fence {
     pub fn is_pause(&self) -> bool {
         self.pred
@@ -393,6 +398,27 @@ impl Display for AmoOp {
     }
 }
 
+impl Debug for DecodeError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("DecodeError")
+            .field("instruction", &format!("{:0>32b}", self.instruction))
+            .field("unexpected_field", &self.unexpected_field)
+            .finish()
+    }
+}
+
+impl Display for DecodeError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "failed to decode instruction '{:0>32b}' because of field '{}'",
+            self.instruction, self.unexpected_field
+        )
+    }
+}
+
+impl std::error::Error for DecodeError {}
+
 fn sign_extend(value: u32, size: u32) -> u32 {
     let right = u32::BITS - size;
     (((value << right) as i32) >> right) as u32
@@ -461,12 +487,6 @@ impl InstCode {
     }
 }
 
-impl Debug for InstCode {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:0>32b}", self.0)
-    }
-}
-
 #[derive(Clone, Copy)]
 pub struct InstCodeC(u16);
 
@@ -537,8 +557,15 @@ pub enum IsCompressed {
     No,
 }
 
+fn decode_error(instruction: impl Into<InstCode>, unexpected_field: &'static str) -> DecodeError {
+    DecodeError {
+        instruction: instruction.into().0,
+        unexpected_field,
+    }
+}
+
 impl Inst {
-    pub fn decode(code: u32) -> Result<(Inst, IsCompressed), Status> {
+    pub fn decode(code: u32) -> Result<(Inst, IsCompressed), DecodeError> {
         let is_compressed = (code & 0b11) != 0b11;
         if is_compressed {
             Ok((Self::decode_compressed(code as u16)?, IsCompressed::Yes))
@@ -547,10 +574,10 @@ impl Inst {
         }
     }
 
-    fn decode_compressed(code: u16) -> Result<Inst, Status> {
+    fn decode_compressed(code: u16) -> Result<Inst, DecodeError> {
         let code = InstCodeC(code);
         if code.0 == 0 {
-            return Err(Status::IllegalInstruction(code.into(), "null instruction"));
+            return Err(decode_error(code, "null instruction"));
         }
         let inst = match code.quadrant() {
             // C0
@@ -573,7 +600,7 @@ impl Inst {
                     src: code.rs2_short(),
                     base: code.rs1_short(),
                 },
-                _ => return Err(Status::IllegalInstruction(code.into(), "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // C1
             0b01 => match code.funct3() {
@@ -610,7 +637,7 @@ impl Inst {
                         // C.SRLI -> srli \rd', \rd', \imm
                         0b00 => {
                             if bit12 != 0 {
-                                return Err(Status::IllegalInstruction(code.into(), "imm"));
+                                return Err(decode_error(code, "imm"));
                             }
 
                             Inst::Srli {
@@ -622,7 +649,7 @@ impl Inst {
                         // C.SRAI -> srai \rd', \rd', \imm
                         0b01 => {
                             if bit12 != 0 {
-                                return Err(Status::IllegalInstruction(code.into(), "imm"));
+                                return Err(decode_error(code, "imm"));
                             }
 
                             Inst::Srai {
@@ -639,7 +666,7 @@ impl Inst {
                         },
                         0b11 => {
                             if bit12 != 0 {
-                                return Err(Status::IllegalInstruction(code.into(), "bit 12"));
+                                return Err(decode_error(code, "bit 12"));
                             }
                             let funct2 = code.extract(5..=6);
                             match funct2 {
@@ -696,6 +723,7 @@ impl Inst {
                                 (3..=4, 7),
                                 (5..=5, 6),
                                 (6..=6, 4),
+                                (12..=12, 9),
                             ]),
                             dest: Reg::SP,
                             src1: Reg::SP,
@@ -704,7 +732,7 @@ impl Inst {
                         _ => {
                             let uimm = code.immediate_s(&[(2..=6, 12), (12..=12, 17)]);
                             if uimm == 0 {
-                                return Err(Status::IllegalInstruction(code.into(), "imm"));
+                                return Err(decode_error(code, "imm"));
                             }
                             Inst::Lui {
                                 uimm,
@@ -737,14 +765,14 @@ impl Inst {
                     src1: code.rs1_short(),
                     src2: Reg::ZERO,
                 },
-                _ => return Err(Status::IllegalInstruction(code.into(), "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // C2
             0b10 => match code.funct3() {
                 // C.SLLI -> slli \rd, \rd, \imm
                 0b000 => {
                     if code.extract(12..=12) != 0 {
-                        return Err(Status::IllegalInstruction(code.into(), "imm"));
+                        return Err(decode_error(code, "imm"));
                     }
                     Inst::Slli {
                         imm: code.immediate_u(&[(2..=6, 0), (12..=12, 5)]),
@@ -756,7 +784,7 @@ impl Inst {
                 0b010 => {
                     let dest = code.rd();
                     if dest.0 == 0 {
-                        return Err(Status::IllegalInstruction(code.into(), "rd"));
+                        return Err(decode_error(code, "rd"));
                     }
 
                     Inst::Lw {
@@ -773,7 +801,7 @@ impl Inst {
                         // C.JR -> jalr zero, 0(\rs1)
                         (0, _, 0) => {
                             if rd_rs1.0 == 0 {
-                                return Err(Status::IllegalInstruction(code.into(), "rs1"));
+                                return Err(decode_error(code, "rs1"));
                             }
                             Inst::Jalr {
                                 offset: 0,
@@ -801,7 +829,7 @@ impl Inst {
                             src1: rd_rs1,
                             src2: rs2,
                         },
-                        _ => return Err(Status::IllegalInstruction(code.into(), "inst")),
+                        _ => return Err(decode_error(code, "inst")),
                     }
                 }
                 // C.SWSP -> sw \reg \offset(sp)
@@ -810,14 +838,14 @@ impl Inst {
                     src: code.rs2(),
                     base: Reg::SP,
                 },
-                _ => return Err(Status::IllegalInstruction(code.into(), "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
-            _ => return Err(Status::IllegalInstruction(code.into(), "op")),
+            _ => return Err(decode_error(code, "op")),
         };
         Ok(inst)
     }
 
-    fn decode_normal(code: u32) -> Result<Inst, Status> {
+    fn decode_normal(code: u32) -> Result<Inst, DecodeError> {
         let code = InstCode(code);
         let inst = match code.opcode() {
             // LUI
@@ -842,7 +870,7 @@ impl Inst {
                     base: code.rs1(),
                     dest: code.rd(),
                 },
-                _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // BRANCH
             0b1100011 => match code.funct3() {
@@ -876,7 +904,7 @@ impl Inst {
                     src1: code.rs1(),
                     src2: code.rs2(),
                 },
-                _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // LOAD
             0b0000011 => match code.funct3() {
@@ -905,7 +933,7 @@ impl Inst {
                     dest: code.rd(),
                     base: code.rs1(),
                 },
-                _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // STORE
             0b0100011 => match code.funct3() {
@@ -924,7 +952,7 @@ impl Inst {
                     src: code.rs2(),
                     base: code.rs1(),
                 },
-                _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // OP-IMM
             0b0010011 => match code.funct3() {
@@ -974,9 +1002,9 @@ impl Inst {
                         dest: code.rd(),
                         src1: code.rs1(),
                     },
-                    _ => return Err(Status::IllegalInstruction(code, "funct7")),
+                    _ => return Err(decode_error(code, "funct7")),
                 },
-                _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                _ => return Err(decode_error(code, "funct3")),
             },
             // OP
             0b0110011 => {
@@ -1001,7 +1029,7 @@ impl Inst {
                     (0b101, 0b0000001) => Inst::Divu { dest, src1, src2 },
                     (0b110, 0b0000001) => Inst::Rem { dest, src1, src2 },
                     (0b111, 0b0000001) => Inst::Remu { dest, src1, src2 },
-                    _ => return Err(Status::IllegalInstruction(code, "funct3/funct7")),
+                    _ => return Err(decode_error(code, "funct3/funct7")),
                 }
             }
             // MISC-MEM
@@ -1030,34 +1058,34 @@ impl Inst {
                             src: code.rs1(),
                         },
                     },
-                    _ => return Err(Status::IllegalInstruction(code, "funct3")),
+                    _ => return Err(decode_error(code, "funct3")),
                 }
             }
             // SYSTEM
             0b1110011 => {
                 if code.0 == 0b11000000000000000001000001110011 {
-                    return Err(Status::Trap("unimp instruction"));
+                    return Err(decode_error(code, "unimp instruction"));
                 }
                 if code.rd().0 != 0 {
-                    return Err(Status::IllegalInstruction(code, "rd"));
+                    return Err(decode_error(code, "rd"));
                 }
                 if code.funct3() != 0 {
-                    return Err(Status::IllegalInstruction(code, "funct3"));
+                    return Err(decode_error(code, "funct3"));
                 }
                 if code.rs1().0 != 0 {
-                    return Err(Status::IllegalInstruction(code, "rs1"));
+                    return Err(decode_error(code, "rs1"));
                 }
                 match code.imm_i() {
                     0b000000000000 => Inst::Ecall,
                     0b000000000001 => Inst::Ebreak,
-                    _ => return Err(Status::IllegalInstruction(code, "imm")),
+                    _ => return Err(decode_error(code, "imm")),
                 }
             }
             // AMO
             0b00101111 => {
                 // width must be W
                 if code.funct3() != 0b010 {
-                    return Err(Status::IllegalInstruction(code, "funct3"));
+                    return Err(decode_error(code, "funct3"));
                 }
 
                 let kind = code.extract(27..=31);
@@ -1070,7 +1098,7 @@ impl Inst {
                     // LR
                     0b00010 => {
                         if code.rs2().0 != 0 {
-                            return Err(Status::IllegalInstruction(code, "rs2"));
+                            return Err(decode_error(code, "rs2"));
                         }
 
                         Inst::LrW {
@@ -1097,7 +1125,7 @@ impl Inst {
                             0b10100 => AmoOp::Max,
                             0b11000 => AmoOp::Minu,
                             0b11100 => AmoOp::Maxu,
-                            _ => return Err(Status::IllegalInstruction(code, "funct7")),
+                            _ => return Err(decode_error(code, "funct7")),
                         };
                         Inst::AmoW {
                             order,
@@ -1109,7 +1137,7 @@ impl Inst {
                     }
                 }
             }
-            _ => return Err(Status::IllegalInstruction(code, "opcode")),
+            _ => return Err(decode_error(code, "opcode")),
         };
         Ok(inst)
     }
diff --git a/src/lib.rs b/src/lib.rs
index 5151fb3..b05365a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,6 +10,7 @@ const MEMORY_SIZE: usize = 2 << 21;
 pub fn execute_linux_elf(
     elf: &[u8],
     debug: bool,
+    break_addr: u32,
     ecall_handler: Box<dyn FnMut(&mut emu::Memory, &mut [u32; 32]) -> Result<(), emu::Status>>,
 ) -> eyre::Result<emu::Status> {
     let elf = elf::Elf { content: elf };
@@ -67,9 +68,10 @@ pub fn execute_linux_elf(
         xreg0_value: 0,
         pc: start,
         reservation_set: None,
-        
+
         is_breaking: false,
 
+        break_pc: break_addr,
         debug,
         ecall_handler,
     };
diff --git a/src/main.rs b/src/main.rs
index f4c8e81..ecf03be 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,17 +1,36 @@
+use std::io::Write;
+
 use eyre::eyre;
 use rustv32i::emu::{self, Memory, Reg};
 
 fn main() -> eyre::Result<()> {
     let content = std::fs::read(std::env::args().nth(1).unwrap()).unwrap();
 
+    let break_addr = std::env::args()
+        .skip_while(|arg| arg != "--break")
+        .nth(1)
+        .map(|addr| {
+            if let Some(addr) = addr.strip_prefix("0x") {
+                u32::from_str_radix(addr, 16)
+            } else {
+                u32::from_str_radix(&addr, 10)
+            }
+        })
+        .unwrap_or(Ok(0))?;
+
+    let debug = std::env::args().any(|arg| arg == "--debug");
+
     let mut syscall_state = SyscallState { set_child_tid: 0 };
 
     let status = rustv32i::execute_linux_elf(
         &content,
-        std::env::args().any(|arg| arg == "--debug"),
+        debug,
+        break_addr,
         Box::new(move |mem, xreg| ecall_handler(mem, xreg, &mut syscall_state)),
     )?;
 
+    std::io::stdout().flush()?;
+
     match status {
         emu::Status::Exit { code } => {
             eprintln!("exited with code {code}");
diff --git a/tests/check.rs b/tests/check.rs
index 7388bec..823ab24 100644
--- a/tests/check.rs
+++ b/tests/check.rs
@@ -47,6 +47,7 @@ fn test_case(tmpdir: &Path, file: &DirEntry, name: &str, march: &str) -> eyre::R
     let status = rustv32i::execute_linux_elf(
         &content,
         true,
+        0,
         Box::new(|_, xreg| {
             if xreg[Reg::A7.0 as usize] == u32::MAX {
                 if xreg[Reg::A0.0 as usize] == 1 {
diff --git a/tests/check/int_comp.S b/tests/check/int_comp.S
index 317535b..71753fa 100644
--- a/tests/check/int_comp.S
+++ b/tests/check/int_comp.S
@@ -2,36 +2,75 @@
 
 #include "../helper.S"
 
-.macro CASER inst a b expected
+.macro CASER inst:req a:req b:req expected:req
     li t0, \a
     li t1, \b
     \inst t2, t0, t1
     ASSERT_EQ t2, \expected
 .endm
 
-.macro CASE_IMM inst a b expected
+.macro CASE_IMM inst:req a:req b:req expected:req
     li t0, \a
     \inst t2, t0, \b
     ASSERT_EQ t2, \expected
 .endm
 
-.macro CASE_BOTH inst insti a b expected
+.macro CASE_BOTH inst:req insti:req a:req b:req expected:req
     CASER \inst, \a, \b, \expected
     CASE_IMM \insti, \a, \b, \expected
 .endm
 
-
-.macro CASE inst a b expected
+.macro CASE inst:req a:req b:req expected:req
     CASE_BOTH \inst, \inst\()i, \a, \b, \expected
 .endm
 
+.macro WITH_SINGLE_TEST_NUMBERS macro
+    \macro a, 0
+    \macro c, 1
+    \macro d, 2
+    \macro u, 3
+    \macro e, 4
+    \macro v, 5
+    \macro f, 8
+    \macro t, 10
+    \macro g, 16
+    \macro h, 32
+    \macro i, 64
+    \macro s, 100
+    \macro j, 128
+    \macro k, 256
+    \macro l, 512
+    \macro w, 1000
+    \macro m, 1024
+    \macro n, 2047
+    \macro b, -1
+    \macro o, -2
+    \macro p, -16
+    \macro q, -1024
+    \macro r, -1000
+
+.endm
+
+.macro WITH_TWO_TEST_NUMBERS macro
+    .macro \macro\()_TMP namea:req a:req
+        .macro \macro\()_TMP_\namea nameb:req b:req
+            \macro \a, \b
+        .endm
+        
+        WITH_SINGLE_TEST_NUMBERS \macro\()_TMP_\namea
+    .endm
+
+    WITH_SINGLE_TEST_NUMBERS \macro\()_TMP
+.endm
+
 START_TEST
     # Base instructions
 
-    CASE add 10, 20, 30
-    CASE add 10, -2, 8
-    CASE add 10, 0, 10
-    CASE add 0, 0, 0
+    .macro CASE_ADD a:req, b:req
+        CASE add, \a, \b, \a + \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_ADD
 
     CASE slt 10 20 1
     CASE slt 20 10 0
@@ -52,15 +91,33 @@ START_TEST
     CASE and, -1, 40, 40
     CASE and, 0b101, 0b100, 0b100
 
+    .macro CASE_AND a:req, b:req
+        CASE and, \a, \b, \a & \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_AND
+
     CASE or, -1, 0, -1
     CASE or, -1, 40, -1
     CASE or, 0, 0, 0
     CASE or, 0b101, 0b110, 0b111
 
+    .macro CASE_OR a:req, b:req
+        CASE or, \a, \b, \a | \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_OR
+
     CASE xor, -1, 0, -1
     CASE xor, -1, -1, 0
     CASE xor 0b101, 0b100, 0b001
 
+    .macro CASE_XOR a:req, b:req
+        CASE xor, \a, \b, \a ^ \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_XOR
+
     CASE sll, 2, 1, 4
     CASE sll, 2, 20, 2097152
     CASE sll, 2, 30, 2147483648
@@ -84,6 +141,12 @@ START_TEST
     CASER sub, -1, -2, 1
     CASER sub, 0, 4294967295, 1
 
+    .macro CASE_SUB a:req, b:req
+        CASER sub, \a, \b, \a - \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_SUB
+
     CASE sra, 4, 1, 2
     CASE sra, 0, 10, 0
     CASE sra, 10, 0, 10
@@ -100,6 +163,12 @@ START_TEST
     CASER mul, -1, -1, 1
     CASER mul, 25252566, 5225225, 353909638
 
+    .macro CASE_MUL a:req, b:req
+        CASER mul, \a, \b, \a * \b
+    .endm
+
+    WITH_TWO_TEST_NUMBERS CASE_MUL
+
     CASER mulh 4, 4, 0
     CASER mulh, -1, -1, 0
     CASER mulh, 25252566, 5225225, 30722
diff --git a/tests/check/stack.S b/tests/check/stack.S
new file mode 100644
index 0000000..decd416
--- /dev/null
+++ b/tests/check/stack.S
@@ -0,0 +1,57 @@
+# Stack Pointer Addition (special-cased by compressed instructions)
+# I've had two bugs in this area before...
+
+#include "../helper.S"
+
+.macro CASE_FOR_REGISTER reg:req number:req
+    li \reg, 0
+    addi \reg, \reg, \number
+    ASSERT_EQ \reg, \number
+.endm
+
+# The goal is sp addition, but why not test some other registers as well while we're at it :)
+
+.macro CASE number
+    CASE_FOR_REGISTER sp, \number
+    CASE_FOR_REGISTER ra, \number
+    CASE_FOR_REGISTER a0, \number
+    CASE_FOR_REGISTER s0, \number
+    CASE_FOR_REGISTER t0, \number
+.endm
+
+START_TEST
+    CASE 0
+    CASE 1
+    CASE 2
+    CASE 4
+    CASE 8
+    CASE 10
+    CASE 16
+    CASE 32
+    CASE 64
+    CASE 100
+    CASE 128
+    CASE 200
+    CASE 256
+    CASE 512
+    CASE 1024
+    CASE 2047
+
+    CASE -1
+    CASE -2
+    CASE -4
+    CASE -8
+    CASE -10
+    CASE -16
+    CASE -32
+    CASE -64
+    CASE -100
+    CASE -128
+    CASE -200
+    CASE -256
+    CASE -512
+    CASE -1024
+    CASE -2047
+    CASE -2048
+
+    PASS
diff --git a/tests/helper.S b/tests/helper.S
index 286a001..de1e7ca 100644
--- a/tests/helper.S
+++ b/tests/helper.S
@@ -20,7 +20,6 @@
 .endm
 
 fail:
-    ebreak
     li a7, -1
     li a0, 0
     ecall