diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 1b7200c53b..93af94af87 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -48,6 +48,29 @@ jobs:
     - run: cmake -S ${{github.workspace}}/examples -B ${{github.workspace}}/examples/build -DCMAKE_BUILD_TYPE=Release
     - run: cmake --build ${{github.workspace}}/examples/build --config Release
 
+  wasm:
+    name: Test on WebAssembly
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: true
+    - name: Install Rust
+      run: rustup update stable --no-self-update && rustup default stable
+    - run: rustup target add wasm32-wasi
+    - run: |
+        tag=v10.0.1
+        curl -LO https://github.com/bytecodealliance/wasmtime/releases/download/${tag}/wasmtime-${tag}-x86_64-linux.tar.xz
+        tar xf wasmtime-${tag}-x86_64-linux.tar.xz
+        echo `pwd`/wasmtime-${tag}-x86_64-linux >> $GITHUB_PATH
+        echo CARGO_TARGET_WASM32_WASI_RUNNER='wasmtime run --dir . --' >> $GITHUB_ENV
+        echo CARGO_BUILD_TARGET='wasm32-wasi' >> $GITHUB_ENV
+    - run: |
+        cargo test --workspace \
+          --exclude fuzz-stats \
+          --exclude wasm-tools-fuzz \
+          --exclude wasm-mutate-stats
+
   rustfmt:
     name: Rustfmt
     runs-on: ubuntu-latest
diff --git a/Cargo.toml b/Cargo.toml
index 61f74b2e41..ccc8dd9dab 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -84,7 +84,6 @@ wasm-smith = { workspace = true, features = ["_internal_cli"], optional = true }
 
 # Dependencies of `shrink`
 wasm-shrink = { workspace = true, features = ["clap"], optional = true }
-is_executable = { version = "1.0.1", optional = true }
 
 # Dependencies of `mutate`
 wasm-mutate = { workspace = true, features = ["clap"], optional = true }
@@ -117,6 +116,9 @@ wit-smith = { workspace = true, features = ["clap"], optional = true }
 addr2line = { version = "0.20.0", optional = true }
 gimli = { version = "0.27.2", optional = true }
 
+[target.'cfg(not(target_family = "wasm"))'.dependencies]
+is_executable = { version = "1.0.1", optional = true }
+
 [dev-dependencies]
 serde_json = "1.0"
 tempfile = "3.1"
diff --git a/crates/wasm-compose/tests/compose.rs b/crates/wasm-compose/tests/compose.rs
index a8344958ad..ff2ed13eaa 100644
--- a/crates/wasm-compose/tests/compose.rs
+++ b/crates/wasm-compose/tests/compose.rs
@@ -1,6 +1,7 @@
 use anyhow::{bail, Context, Result};
 use pretty_assertions::assert_eq;
 use std::fs;
+use std::io;
 use wasm_compose::{composer::ComponentComposer, config::Config};
 use wasmparser::{Validator, WasmFeatures};
 
@@ -51,13 +52,29 @@ fn component_composing() -> Result<()> {
         let (output, baseline_path) = if error_path.is_file() {
             match r {
                 Ok(_) => bail!("composition should fail for test case `{}`", test_case),
-                Err(e) => (
-                    format!("{:?}", e).replace('\\', "/").replace(
-                        "The system cannot find the file specified.",
-                        "No such file or directory",
-                    ),
-                    &error_path,
-                ),
+                Err(e) => {
+                    let mut err = format!("{e}");
+                    let causes = e.chain();
+                    let ncauses = causes.len();
+                    if ncauses > 1 {
+                        err.push_str("\n\nCaused by:");
+                    }
+                    for (i, cause) in causes.skip(1).enumerate() {
+                        err.push_str("\n    ");
+                        if ncauses > 2 {
+                            err.push_str(&format!("{i}: "))
+                        }
+                        match cause.downcast_ref::<io::Error>() {
+                            Some(_) => {
+                                err.push_str("platform-specific error");
+                            }
+                            None => {
+                                err.push_str(&cause.to_string());
+                            }
+                        }
+                    }
+                    (err.replace('\\', "/"), &error_path)
+                }
             }
         } else {
             let bytes =
diff --git a/crates/wasm-compose/tests/compositions/component-missing/error.txt b/crates/wasm-compose/tests/compositions/component-missing/error.txt
index dde33c0936..8b88baf34a 100644
--- a/crates/wasm-compose/tests/compositions/component-missing/error.txt
+++ b/crates/wasm-compose/tests/compositions/component-missing/error.txt
@@ -2,4 +2,4 @@ failed to parse component `tests/compositions/component-missing/a.wat`
 
 Caused by:
     0: failed to read from `tests/compositions/component-missing/a.wat`
-    1: No such file or directory (os error 2)
+    1: platform-specific error
diff --git a/crates/wasm-compose/tests/compositions/component-not-wat/error.txt b/crates/wasm-compose/tests/compositions/component-not-wat/error.txt
index 39d3ab0458..8d8d29ed84 100644
--- a/crates/wasm-compose/tests/compositions/component-not-wat/error.txt
+++ b/crates/wasm-compose/tests/compositions/component-not-wat/error.txt
@@ -2,7 +2,7 @@ failed to parse component `tests/compositions/component-not-wat/root.wat`
 
 Caused by:
     expected `(`
-         --> tests/compositions/component-not-wat/root.wat:1:1
-          |
-        1 | not valid
-          | ^
+     --> tests/compositions/component-not-wat/root.wat:1:1
+      |
+    1 | not valid
+      | ^
diff --git a/crates/wasm-compose/tests/compositions/missing-explicit-dep/error.txt b/crates/wasm-compose/tests/compositions/missing-explicit-dep/error.txt
index 415ffcae6f..ed7bb6813f 100644
--- a/crates/wasm-compose/tests/compositions/missing-explicit-dep/error.txt
+++ b/crates/wasm-compose/tests/compositions/missing-explicit-dep/error.txt
@@ -2,4 +2,4 @@ failed to parse component `tests/compositions/missing-explicit-dep/a.wat`
 
 Caused by:
     0: failed to read from `tests/compositions/missing-explicit-dep/a.wat`
-    1: No such file or directory (os error 2)
+    1: platform-specific error
diff --git a/crates/wasm-compose/tests/compositions/missing-root/error.txt b/crates/wasm-compose/tests/compositions/missing-root/error.txt
index 82aefdb9c3..d3d92144f4 100644
--- a/crates/wasm-compose/tests/compositions/missing-root/error.txt
+++ b/crates/wasm-compose/tests/compositions/missing-root/error.txt
@@ -2,4 +2,4 @@ failed to parse component `tests/compositions/missing-root/root.wat`
 
 Caused by:
     0: failed to read from `tests/compositions/missing-root/root.wat`
-    1: No such file or directory (os error 2)
+    1: platform-specific error
diff --git a/crates/wasm-mutate/src/mutators.rs b/crates/wasm-mutate/src/mutators.rs
index 4c96c87b74..23e5e2c1fa 100644
--- a/crates/wasm-mutate/src/mutators.rs
+++ b/crates/wasm-mutate/src/mutators.rs
@@ -136,7 +136,7 @@ impl WasmMutate<'_> {
 
         assert!(can_mutate);
 
-        let attempts = 100;
+        let attempts = 2000;
         let mut last_mutation = None;
 
         for _ in 0..attempts {
diff --git a/crates/wasm-mutate/src/mutators/peephole.rs b/crates/wasm-mutate/src/mutators/peephole.rs
index 41ef663d8a..9110da9a2c 100644
--- a/crates/wasm-mutate/src/mutators/peephole.rs
+++ b/crates/wasm-mutate/src/mutators/peephole.rs
@@ -569,6 +569,7 @@ mod tests {
 
     /// Condition to apply the unfold operator
     /// check that the var is a constant
+    #[allow(dead_code)]
     fn is_const(vari: &'static str) -> impl Fn(&mut EG, Id, &Subst) -> bool {
         move |egraph: &mut EG, _, subst| {
             let var = vari.parse();
@@ -608,7 +609,11 @@ mod tests {
         }
     }
 
+    // Random numbers vary by pointer-width presumably due to `usize` at some
+    // point factoring in, and this test is only known to pass within a
+    // reasonable amount of time on 64-bit platforms.
     #[test]
+    #[cfg(target_pointer_width = "64")]
     fn test_peep_unfold2() {
         let rules: &[Rewrite<super::Lang, PeepholeMutationAnalysis>] = &[
             rewrite!("unfold-2";  "?x" => "(i32.unfold ?x)" if is_const("?x") if is_type("?x", PrimitiveTypeInfo::I32)),
@@ -1588,7 +1593,7 @@ mod tests {
         seed: u64,
     ) {
         let mut config = WasmMutate::default();
-        config.fuel(300);
+        config.fuel(10000);
         config.seed(seed);
 
         let mutator = PeepholeMutator::new_with_rules(3, rules.to_vec());
diff --git a/crates/wasm-smith/Cargo.toml b/crates/wasm-smith/Cargo.toml
index 5d2116a653..20385676dd 100644
--- a/crates/wasm-smith/Cargo.toml
+++ b/crates/wasm-smith/Cargo.toml
@@ -26,10 +26,12 @@ wasmparser = { workspace = true }
 
 [dev-dependencies]
 criterion = { workspace = true }
-libfuzzer-sys = { workspace = true }
 rand = { workspace = true }
 wasmprinter = { path = "../wasmprinter" }
 wat = { path = "../wat" }
 
+[target.'cfg(not(target_family = "wasm"))'.dev-dependencies]
+libfuzzer-sys = { workspace = true }
+
 [features]
 _internal_cli = ["serde", "flagset/serde"]
diff --git a/crates/wast/src/core/expr.rs b/crates/wast/src/core/expr.rs
index 0f79d68a00..01316f9688 100644
--- a/crates/wast/src/core/expr.rs
+++ b/crates/wast/src/core/expr.rs
@@ -1155,8 +1155,8 @@ instructions! {
 // ideally it also wouldn't be as large as it is now.
 const _: () = {
     let size = std::mem::size_of::<Instruction<'_>>();
-    let pointer = std::mem::size_of::<usize>();
-    assert!(size <= pointer * 20);
+    let pointer = std::mem::size_of::<u64>();
+    assert!(size <= pointer * 10);
 };
 
 impl<'a> Instruction<'a> {
diff --git a/crates/wast/src/lexer.rs b/crates/wast/src/lexer.rs
index 0888646c8f..f588ec2f15 100644
--- a/crates/wast/src/lexer.rs
+++ b/crates/wast/src/lexer.rs
@@ -61,7 +61,7 @@ pub struct Token {
 }
 
 const _: () = {
-    assert!(std::mem::size_of::<Token>() <= std::mem::size_of::<usize>() * 4);
+    assert!(std::mem::size_of::<Token>() <= std::mem::size_of::<u64>() * 2);
 };
 
 /// Classification of what was parsed from the input stream.
diff --git a/src/bin/wasm-tools/main.rs b/src/bin/wasm-tools/main.rs
index e176f6713d..70c2849dd3 100644
--- a/src/bin/wasm-tools/main.rs
+++ b/src/bin/wasm-tools/main.rs
@@ -7,10 +7,11 @@ use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
 macro_rules! subcommands {
     ($(
         $(#[$attr:meta])*
-        ($name:ident, $string:tt)
+        ($name:ident, $string:tt $($cfg:tt)*)
     )*) => {
         $(
             #[cfg(feature = $string)]
+            $($cfg)*
             mod $name;
         )*
 
@@ -20,6 +21,7 @@ macro_rules! subcommands {
         enum WasmTools {
             $(
                 #[cfg(feature = $string)]
+                $($cfg)*
                 $(#[$attr])*
                 $name($name::Opts),
             )*
@@ -30,6 +32,7 @@ macro_rules! subcommands {
                 match self {
                     $(
                         #[cfg(feature = $string)]
+                        $($cfg)*
                         Self::$name(opts) => opts.run(),
                     )*
                 }
@@ -39,6 +42,7 @@ macro_rules! subcommands {
                 match *self {
                     $(
                         #[cfg(feature = $string)]
+                        $($cfg)*
                         Self::$name(ref opts) => opts.general_opts(),
                     )*
                 }
@@ -52,7 +56,10 @@ subcommands! {
     (validate, "validate")
     (print, "print")
     (smith, "smith")
-    (shrink, "shrink")
+    // The shrink subcommand relies on executing new processes to test a
+    // predicate which isn't supported on wasm, so always omit this command on
+    // wasm.
+    (shrink, "shrink" #[cfg(not(target_family = "wasm"))])
     (mutate, "mutate")
     (dump, "dump")
     (objdump, "objdump")
diff --git a/tests/cli.rs b/tests/cli.rs
index c8d8a0e3fd..b9bb53c03e 100644
--- a/tests/cli.rs
+++ b/tests/cli.rs
@@ -34,6 +34,12 @@ use std::path::{Path, PathBuf};
 use std::process::{Command, Output, Stdio};
 
 fn main() {
+    // This test suite can't run on wasm since it involves spawning
+    // subprocesses.
+    if cfg!(target_family = "wasm") {
+        return;
+    }
+
     let mut tests = Vec::new();
     find_tests("tests/cli".as_ref(), &mut tests);
     let filter = std::env::args().nth(1);