diff --git a/ezcache_test.go b/ezcache_test.go
new file mode 100644
index 0000000..127bc65
--- /dev/null
+++ b/ezcache_test.go
@@ -0,0 +1,44 @@
+package ezcache_test
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"codeberg.org/danjones000/ezcache"
+	"github.com/stretchr/testify/assert"
+)
+
+var fetcher ezcache.Fetcher[uint8, string] = func(key uint8) (string, error) { return fmt.Sprintf("%d", key), nil }
+
+func TestNewHappy(t *testing.T) {
+	cache, err := ezcache.New(fetcher, 1)
+
+	assert.NoError(t, err)
+	assert.NotNil(t, cache)
+}
+
+func TestNewNilFetcher(t *testing.T) {
+	cache, err := ezcache.New[uint8, string](nil, 1)
+
+	assert.ErrorIs(t, err, ezcache.ErrInvalidFetcher)
+	assert.Nil(t, cache)
+}
+
+func TestNewBadExpiry(tt *testing.T) {
+	testcases := []struct {
+		name string
+		exp  time.Duration
+	}{
+		{"zero", 0},
+		{"negative", -5},
+	}
+	for _, tc := range testcases {
+		tt.Run(tc.name, func(t *testing.T) {
+			cache, err := ezcache.New(fetcher, tc.exp)
+
+			assert.ErrorIs(t, err, ezcache.ErrInvalidExpiry)
+			assert.Nil(t, cache)
+		})
+	}
+}
diff --git a/go.mod b/go.mod
index a4a9bfa..6718616 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,11 @@
 module codeberg.org/danjones000/ezcache
 
 go 1.23.7
+
+require github.com/stretchr/testify v1.10.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..713a0b4
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=