diff --git a/wasmtime-environ/Cargo.toml b/wasmtime-environ/Cargo.toml
index 87364eef0d..a1e994ce4a 100644
--- a/wasmtime-environ/Cargo.toml
+++ b/wasmtime-environ/Cargo.toml
@@ -29,6 +29,12 @@ lazy_static = "1.3.0"
 spin = "0.5.0"
 log = { version = "0.4.8", default-features = false }
 
+[dev-dependencies]
+tempfile = "3"
+target-lexicon = { version = "0.4.0", default-features = false }
+pretty_env_logger = "0.3.0"
+rand = { version = "0.7.0", features = ["small_rng"] }
+
 [features]
 default = ["std"]
 std = ["cranelift-codegen/std", "cranelift-wasm/std"]
diff --git a/wasmtime-environ/src/address_map.rs b/wasmtime-environ/src/address_map.rs
index cf4876e435..8c3c53be80 100644
--- a/wasmtime-environ/src/address_map.rs
+++ b/wasmtime-environ/src/address_map.rs
@@ -8,7 +8,7 @@ use serde::{Deserialize, Serialize};
 use std::vec::Vec;
 
 /// Single source location to generated address mapping.
-#[derive(Serialize, Deserialize, Debug, Clone)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 pub struct InstructionAddressMap {
     /// Original source location.
     pub srcloc: ir::SourceLoc,
@@ -21,7 +21,7 @@ pub struct InstructionAddressMap {
 }
 
 /// Function and its instructions addresses mappings.
-#[derive(Serialize, Deserialize, Debug, Clone)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 pub struct FunctionAddressMap {
     /// Instructions maps.
     /// The array is sorted by the InstructionAddressMap::code_offset field.
diff --git a/wasmtime-environ/src/cache.rs b/wasmtime-environ/src/cache.rs
index 8dcd7df9b4..eff8d07141 100644
--- a/wasmtime-environ/src/cache.rs
+++ b/wasmtime-environ/src/cache.rs
@@ -159,7 +159,7 @@ pub struct ModuleCacheEntry {
     mod_cache_path: Option<PathBuf>,
 }
 
-#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(serde::Serialize, serde::Deserialize, Debug)]
 pub struct ModuleCacheData {
     compilation: Compilation,
     relocations: Relocations,
@@ -505,3 +505,6 @@ impl<'de> Deserialize<'de> for JtOffsetsWrapper<'_> {
         deserializer.deserialize_seq(JtOffsetsWrapperVisitor {})
     }
 }
+
+#[cfg(test)]
+mod tests;
diff --git a/wasmtime-environ/src/cache/tests.rs b/wasmtime-environ/src/cache/tests.rs
new file mode 100644
index 0000000000..52fc7bba5c
--- /dev/null
+++ b/wasmtime-environ/src/cache/tests.rs
@@ -0,0 +1,325 @@
+use super::*;
+use crate::address_map::{FunctionAddressMap, InstructionAddressMap};
+use crate::compilation::{Relocation, RelocationTarget};
+use crate::module::{MemoryPlan, MemoryStyle, Module};
+use cranelift_codegen::ir::entities::JumpTable;
+use cranelift_codegen::{binemit, ir, isa, settings, ValueLocRange};
+use cranelift_entity::EntityRef;
+use cranelift_entity::{PrimaryMap, SecondaryMap};
+use cranelift_wasm::{DefinedFuncIndex, FuncIndex, Global, GlobalInit, Memory, SignatureIndex};
+use rand::rngs::SmallRng;
+use rand::{Rng, SeedableRng};
+use std::boxed::Box;
+use std::cmp::{max, min};
+use std::fs;
+use std::str::FromStr;
+use std::vec::Vec;
+use target_lexicon::triple;
+use tempfile;
+
+// Since cache system is a global thing, each test needs to be run in seperate process.
+// So, init() tests are run as integration tests.
+// However, caching is a private thing, an implementation detail, and needs to be tested
+// from the inside of the module. Thus we have one big test here.
+
+#[test]
+fn test_write_read_cache() {
+    pretty_env_logger::init();
+    let dir = tempfile::tempdir().expect("Can't create temporary directory");
+    conf::init(true, Some(dir.path()));
+    assert!(conf::cache_enabled());
+    // assumption: config init creates cache directory and returns canonicalized path
+    assert_eq!(
+        *conf::cache_directory(),
+        fs::canonicalize(dir.path()).unwrap()
+    );
+
+    let mut rng = SmallRng::from_seed([
+        0x42, 0x04, 0xF3, 0x44, 0x11, 0x22, 0x33, 0x44, 0x67, 0x68, 0xFF, 0x00, 0x44, 0x23, 0x7F,
+        0x96,
+    ]);
+
+    let mut code_container = Vec::new();
+    code_container.resize(0x4000, 0);
+    rng.fill(&mut code_container[..]);
+
+    let isa1 = new_isa("riscv64");
+    let isa2 = new_isa("i386");
+    let module1 = new_module(&mut rng);
+    let module2 = new_module(&mut rng);
+    let function_body_inputs1 = new_function_body_inputs(&mut rng, &code_container);
+    let function_body_inputs2 = new_function_body_inputs(&mut rng, &code_container);
+    let compiler1 = "test-1";
+    let compiler2 = "test-2";
+
+    let entry1 = ModuleCacheEntry::new(&module1, &function_body_inputs1, &*isa1, compiler1, false);
+    assert!(entry1.mod_cache_path().is_some());
+    assert!(entry1.get_data().is_none());
+    let data1 = new_module_cache_data(&mut rng);
+    entry1.update_data(&data1);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data1);
+
+    let entry2 = ModuleCacheEntry::new(&module2, &function_body_inputs1, &*isa1, compiler1, false);
+    let data2 = new_module_cache_data(&mut rng);
+    entry2.update_data(&data2);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data1);
+    assert_eq!(entry2.get_data().expect("Cache should be available"), data2);
+
+    let entry3 = ModuleCacheEntry::new(&module1, &function_body_inputs2, &*isa1, compiler1, false);
+    let data3 = new_module_cache_data(&mut rng);
+    entry3.update_data(&data3);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data1);
+    assert_eq!(entry2.get_data().expect("Cache should be available"), data2);
+    assert_eq!(entry3.get_data().expect("Cache should be available"), data3);
+
+    let entry4 = ModuleCacheEntry::new(&module1, &function_body_inputs1, &*isa2, compiler1, false);
+    let data4 = new_module_cache_data(&mut rng);
+    entry4.update_data(&data4);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data1);
+    assert_eq!(entry2.get_data().expect("Cache should be available"), data2);
+    assert_eq!(entry3.get_data().expect("Cache should be available"), data3);
+    assert_eq!(entry4.get_data().expect("Cache should be available"), data4);
+
+    let entry5 = ModuleCacheEntry::new(&module1, &function_body_inputs1, &*isa1, compiler2, false);
+    let data5 = new_module_cache_data(&mut rng);
+    entry5.update_data(&data5);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data1);
+    assert_eq!(entry2.get_data().expect("Cache should be available"), data2);
+    assert_eq!(entry3.get_data().expect("Cache should be available"), data3);
+    assert_eq!(entry4.get_data().expect("Cache should be available"), data4);
+    assert_eq!(entry5.get_data().expect("Cache should be available"), data5);
+
+    let data6 = new_module_cache_data(&mut rng);
+    entry1.update_data(&data6);
+    assert_eq!(entry1.get_data().expect("Cache should be available"), data6);
+    assert_eq!(entry2.get_data().expect("Cache should be available"), data2);
+    assert_eq!(entry3.get_data().expect("Cache should be available"), data3);
+    assert_eq!(entry4.get_data().expect("Cache should be available"), data4);
+    assert_eq!(entry5.get_data().expect("Cache should be available"), data5);
+
+    assert!(data1 != data2 && data1 != data3 && data1 != data4 && data1 != data5 && data1 != data6);
+}
+
+fn new_isa(name: &str) -> Box<dyn isa::TargetIsa> {
+    let shared_builder = settings::builder();
+    let shared_flags = settings::Flags::new(shared_builder);
+    isa::lookup(triple!(name))
+        .expect("can't find specified isa")
+        .finish(shared_flags)
+}
+
+fn new_module(rng: &mut impl Rng) -> Module {
+    // There are way too many fields. Just fill in some of them.
+    let mut m = Module::new();
+
+    if rng.gen_bool(0.5) {
+        m.signatures.push(ir::Signature {
+            params: vec![],
+            returns: vec![],
+            call_conv: isa::CallConv::Fast,
+        });
+    }
+
+    for i in 0..rng.gen_range(1, 0x8) {
+        m.functions.push(SignatureIndex::new(i));
+    }
+
+    if rng.gen_bool(0.8) {
+        m.memory_plans.push(MemoryPlan {
+            memory: Memory {
+                minimum: rng.gen(),
+                maximum: rng.gen(),
+                shared: rng.gen(),
+            },
+            style: MemoryStyle::Dynamic,
+            offset_guard_size: rng.gen(),
+        });
+    }
+
+    if rng.gen_bool(0.4) {
+        m.globals.push(Global {
+            ty: ir::Type::int(16).unwrap(),
+            mutability: rng.gen(),
+            initializer: GlobalInit::I32Const(rng.gen()),
+        });
+    }
+
+    m
+}
+
+fn new_function_body_inputs<'data>(
+    rng: &mut impl Rng,
+    code_container: &'data Vec<u8>,
+) -> PrimaryMap<DefinedFuncIndex, FunctionBodyData<'data>> {
+    let len = code_container.len();
+    let mut pos = rng.gen_range(0, code_container.len());
+    (2..rng.gen_range(4, 14))
+        .map(|j| {
+            let (old_pos, end) = (pos, min(pos + rng.gen_range(0x10, 0x200), len));
+            pos = end % len;
+            FunctionBodyData {
+                data: &code_container[old_pos..end],
+                module_offset: (rng.next_u64() + j) as usize,
+            }
+        })
+        .collect()
+}
+
+fn new_module_cache_data(rng: &mut impl Rng) -> ModuleCacheData {
+    // WARNING: if method changed, update PartialEq impls below, too!
+    let funcs = (0..rng.gen_range(0, 10))
+        .map(|i| {
+            let mut sm = SecondaryMap::new(); // doesn't implement from iterator
+            sm.resize(i as usize * 2);
+            sm.values_mut().enumerate().for_each(|(j, v)| {
+                if rng.gen_bool(0.33) {
+                    *v = (j as u32) * 3 / 4
+                }
+            });
+            CodeAndJTOffsets {
+                body: (0..(i * 3 / 2)).collect(),
+                jt_offsets: sm,
+            }
+        })
+        .collect();
+
+    let relocs = (0..rng.gen_range(1, 0x10))
+        .map(|i| {
+            vec![
+                Relocation {
+                    reloc: binemit::Reloc::X86CallPCRel4,
+                    reloc_target: RelocationTarget::UserFunc(FuncIndex::new(i as usize * 42)),
+                    offset: i + rng.next_u32(),
+                    addend: 0,
+                },
+                Relocation {
+                    reloc: binemit::Reloc::Arm32Call,
+                    reloc_target: RelocationTarget::LibCall(ir::LibCall::CeilF64),
+                    offset: rng.gen_range(4, i + 55),
+                    addend: (42 * i) as i64,
+                },
+            ]
+        })
+        .collect();
+
+    let trans = (4..rng.gen_range(4, 0x10))
+        .map(|i| FunctionAddressMap {
+            instructions: vec![InstructionAddressMap {
+                srcloc: ir::SourceLoc::new(rng.gen()),
+                code_offset: rng.gen(),
+                code_len: i,
+            }],
+            start_srcloc: ir::SourceLoc::new(rng.gen()),
+            end_srcloc: ir::SourceLoc::new(rng.gen()),
+            body_offset: rng.gen(),
+            body_len: 0x31337,
+        })
+        .collect();
+
+    let value_ranges = (4..rng.gen_range(4, 0x10))
+        .map(|i| {
+            (i..i + rng.gen_range(4, 8))
+                .map(|k| {
+                    (
+                        ir::ValueLabel::new(k),
+                        (0..rng.gen_range(0, 4))
+                            .map(|_| ValueLocRange {
+                                loc: ir::ValueLoc::Reg(rng.gen()),
+                                start: rng.gen(),
+                                end: rng.gen(),
+                            })
+                            .collect(),
+                    )
+                })
+                .collect()
+        })
+        .collect();
+
+    let stack_slots = (0..rng.gen_range(0, 0x6))
+        .map(|_| {
+            let mut slots = ir::StackSlots::new();
+            slots.push(ir::StackSlotData {
+                kind: ir::StackSlotKind::SpillSlot,
+                size: rng.gen(),
+                offset: rng.gen(),
+            });
+            slots.frame_size = rng.gen();
+            slots
+        })
+        .collect();
+
+    ModuleCacheData::from_tuple((
+        Compilation::new(funcs),
+        relocs,
+        trans,
+        value_ranges,
+        stack_slots,
+    ))
+}
+
+impl ModuleCacheEntry {
+    pub fn mod_cache_path(&self) -> &Option<PathBuf> {
+        &self.mod_cache_path
+    }
+}
+
+// cranelift's types (including SecondaryMap) doesn't implement PartialEq
+impl PartialEq for ModuleCacheData {
+    fn eq(&self, other: &Self) -> bool {
+        // compilation field
+        if self.compilation.len() != other.compilation.len() {
+            return false;
+        }
+
+        for i in (0..self.compilation.len()).map(DefinedFuncIndex::new) {
+            let lhs = self.compilation.get(i);
+            let rhs = other.compilation.get(i);
+            if lhs.body != rhs.body || lhs.jt_offsets.get_default() != rhs.jt_offsets.get_default()
+            {
+                return false;
+            }
+
+            for j in (0..max(lhs.jt_offsets.len(), rhs.jt_offsets.len())).map(JumpTable::new) {
+                if lhs.jt_offsets.get(j) != rhs.jt_offsets.get(j) {
+                    return false;
+                }
+            }
+        }
+
+        // relocs
+        {
+            if self.relocations.len() != other.relocations.len() {
+                return false;
+            }
+            let it_lhs = self.relocations.iter();
+            let it_rhs = other.relocations.iter();
+            if it_lhs.zip(it_rhs).any(|(lhs, rhs)| lhs != rhs) {
+                return false;
+            }
+        }
+
+        // debug symbols
+        {
+            if self.address_transforms.len() != other.address_transforms.len() {
+                return false;
+            }
+            let it_lhs = self.address_transforms.iter();
+            let it_rhs = other.address_transforms.iter();
+            if it_lhs.zip(it_rhs).any(|(lhs, rhs)| lhs != rhs) {
+                return false;
+            }
+        }
+
+        true
+    }
+}
+
+// binemit::Reloc doesn't implement PartialEq
+impl PartialEq for Relocation {
+    fn eq(&self, other: &Self) -> bool {
+        self.reloc as u64 == other.reloc as u64
+            && self.reloc_target == other.reloc_target
+            && self.offset == other.offset
+            && self.addend == other.addend
+    }
+}
diff --git a/wasmtime-environ/src/compilation.rs b/wasmtime-environ/src/compilation.rs
index c17d4b12c8..27344c2d4d 100644
--- a/wasmtime-environ/src/compilation.rs
+++ b/wasmtime-environ/src/compilation.rs
@@ -108,7 +108,7 @@ pub struct Relocation {
 }
 
 /// Destination function. Can be either user function or some special one, like `memory.grow`.
-#[derive(Serialize, Deserialize, Debug, Copy, Clone)]
+#[derive(Serialize, Deserialize, Debug, Copy, Clone, PartialEq, Eq)]
 pub enum RelocationTarget {
     /// The user function index.
     UserFunc(FuncIndex),
diff --git a/wasmtime-environ/tests/cache_fail_calling_init_twice.rs b/wasmtime-environ/tests/cache_fail_calling_init_twice.rs
new file mode 100644
index 0000000000..9a0645160d
--- /dev/null
+++ b/wasmtime-environ/tests/cache_fail_calling_init_twice.rs
@@ -0,0 +1,10 @@
+use tempfile;
+use wasmtime_environ::cache_conf;
+
+#[test]
+#[should_panic]
+fn test_fail_calling_init_twice() {
+    let dir = tempfile::tempdir().expect("Can't create temporary directory");
+    cache_conf::init(true, Some(dir.path()));
+    cache_conf::init(true, Some(dir.path()));
+}
diff --git a/wasmtime-environ/tests/cache_fail_usage_without_init.rs b/wasmtime-environ/tests/cache_fail_usage_without_init.rs
new file mode 100644
index 0000000000..b428d9f7fb
--- /dev/null
+++ b/wasmtime-environ/tests/cache_fail_usage_without_init.rs
@@ -0,0 +1,7 @@
+use wasmtime_environ::cache_conf;
+
+#[test]
+#[should_panic]
+fn test_fail_usage_without_init() {
+    let _ = cache_conf::cache_directory();
+}