diff --git a/provide_gaps_test.go b/provide_gaps_test.go
new file mode 100644
index 0000000..8157a32
--- /dev/null
+++ b/provide_gaps_test.go
@@ -0,0 +1,215 @@
+package vessel
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/xraph/go-utils/di"
+)
+
+type gapHandler interface{ ID() string }
+
+type gapA struct{}
+
+func (gapA) ID() string { return "a" }
+
+type gapB struct{}
+
+func (gapB) ID() string { return "b" }
+
+func newGapA() gapHandler { return gapA{} }
+
+func newGapB() *gapB { return &gapB{} }
+
+func TestProvideValue_And_Inject(t *testing.T) {
+	c := New()
+	cfg := &testLogger{level: "debug"}
+
+	require.NoError(t, ProvideValue(c, cfg))
+
+	got, err := Inject[*testLogger](c)
+	require.NoError(t, err)
+	assert.Same(t, cfg, got)
+	assert.True(t, HasType[*testLogger](c))
+}
+
+func TestProvideValue_Named(t *testing.T) {
+	c := New()
+
+	require.NoError(t, ProvideValue(c, &testLogger{level: "warn"}, WithName("audit")))
+
+	got, err := InjectNamed[*testLogger](c, "audit")
+	require.NoError(t, err)
+	assert.Equal(t, "warn", got.level)
+	assert.True(t, HasTypeNamed[*testLogger](c, "audit"))
+	assert.False(t, HasTypeNamed[*testLogger](c, "other"))
+}
+
+func TestProvideNamed_ResolvesByName(t *testing.T) {
+	c := New()
+
+	require.NoError(t, ProvideNamed(c, "primary", newTestDatabase))
+
+	got, err := InjectNamed[*testDatabase](c, "primary")
+	require.NoError(t, err)
+	assert.NotEmpty(t, got.connStr)
+}
+
+func TestDeprecatedProvideAndInjectWrappers(t *testing.T) {
+	c := New()
+
+	require.NoError(t, ProvideConstructor(c, newTestDatabase))
+
+	got, err := InjectType[*testDatabase](c)
+	require.NoError(t, err)
+	assert.NotNil(t, got)
+	assert.Same(t, got, MustInjectType[*testDatabase](c))
+}
+
+func TestProvide_LifecycleOptions(t *testing.T) {
+	t.Run("singleton returns the same instance", func(t *testing.T) {
+		c := New()
+		require.NoError(t, Provide(c, newTestDatabase, AsSingleton()))
+
+		first := MustInject[*testDatabase](c)
+		second := MustInject[*testDatabase](c)
+		assert.Same(t, first, second)
+	})
+
+	t.Run("scoped registers", func(t *testing.T) {
+		c := New()
+		require.NoError(t, Provide(c, newTestDatabase, AsScoped()))
+		assert.True(t, HasType[*testDatabase](c))
+	})
+}
+
+func TestInjectGroup(t *testing.T) {
+	c := New()
+
+	require.NoError(t, Provide(c, newGapA, AsGroup("handlers")))
+	require.NoError(t, Provide(c, newGapB, AsGroup("handlers")))
+
+	t.Run("collects every member", func(t *testing.T) {
+		handlers, err := InjectGroup[gapHandler](c, "handlers")
+		require.NoError(t, err)
+		require.Len(t, handlers, 2)
+
+		ids := []string{handlers[0].ID(), handlers[1].ID()}
+		assert.ElementsMatch(t, []string{"a", "b"}, ids)
+		assert.Len(t, MustInjectGroup[gapHandler](c, "handlers"), 2)
+	})
+
+	t.Run("empty group is not an error", func(t *testing.T) {
+		handlers, err := InjectGroup[gapHandler](c, "missing")
+		require.NoError(t, err)
+		assert.Empty(t, handlers)
+	})
+
+	t.Run("wrong element type is reported", func(t *testing.T) {
+		_, err := InjectGroup[*testDatabase](c, "handlers")
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "type mismatch")
+	})
+}
+
+func TestInjectGroup_NoRegistry(t *testing.T) {
+	c := New().(*containerImpl)
+	c.typeRegistry = nil
+
+	_, err := InjectGroup[gapHandler](c, "handlers")
+	require.Error(t, err)
+
+	assert.Panics(t, func() { MustInjectGroup[gapHandler](c, "handlers") })
+}
+
+func TestResolveGroup(t *testing.T) {
+	c := New().(*containerImpl)
+	param := paramInfo{
+		typ:      reflect.TypeFor[[]gapHandler](),
+		group:    true,
+		groupKey: "handlers",
+	}
+
+	t.Run("no registry", func(t *testing.T) {
+		c.typeRegistry = nil
+
+		_, err := resolveGroup(param, c)
+		require.Error(t, err)
+
+		param.optional = true
+		got, err := resolveGroup(param, c)
+		require.NoError(t, err)
+		assert.Nil(t, got)
+
+		param.optional = false
+	})
+
+	t.Run("empty group", func(t *testing.T) {
+		c.typeRegistry = newTypeRegistry()
+
+		_, err := resolveGroup(param, c)
+		require.Error(t, err)
+
+		param.optional = true
+		got, err := resolveGroup(param, c)
+		require.NoError(t, err)
+		assert.Nil(t, got)
+
+		param.optional = false
+	})
+
+	t.Run("populated group", func(t *testing.T) {
+		c.typeRegistry = nil
+		require.NoError(t, Provide(c, newGapA, AsGroup("handlers")))
+
+		got, err := resolveGroup(param, c)
+		require.NoError(t, err)
+		assert.Len(t, got.([]gapHandler), 1)
+	})
+}
+
+func TestHasType_UnregisteredAndNoRegistry(t *testing.T) {
+	c := New()
+	assert.False(t, HasType[*testDatabase](c))
+
+	impl := c.(*containerImpl)
+	impl.typeRegistry = nil
+	assert.False(t, HasType[*testDatabase](c))
+	assert.False(t, HasTypeNamed[*testDatabase](c, "x"))
+}
+
+func TestDeriveServiceName(t *testing.T) {
+	assert.Equal(t, "custom", deriveServiceName(typeKey{typ: reflect.TypeFor[*testDatabase](), name: "custom"}))
+	assert.Equal(t, "github.com/xraph/vessel.testDatabase", deriveServiceName(typeKey{typ: reflect.TypeFor[*testDatabase]()}))
+	assert.Equal(t, "string", deriveServiceName(typeKey{typ: reflect.TypeFor[string]()}))
+}
+
+func TestErrTypeMismatch(t *testing.T) {
+	err := ErrTypeMismatch("db", 42)
+
+	assert.Equal(t, CodeTypeMismatch, err.Code)
+	assert.Contains(t, err.Error(), "db")
+	assert.Contains(t, err.Error(), "int")
+}
+
+func TestDependencyGraph_Lookups(t *testing.T) {
+	g := NewDependencyGraph()
+	deps := []di.Dep{{Name: "db"}, {Name: "cache", Mode: di.DepLazy}}
+	g.AddNodeWithDeps("svc", deps)
+
+	assert.Equal(t, []string{"db", "cache"}, g.GetDependencies("svc"))
+	assert.Nil(t, g.GetDependencies("unknown"))
+
+	assert.Equal(t, deps, g.GetDeps("svc"))
+	assert.Nil(t, g.GetDeps("unknown"))
+}
+
+func TestWrapperNames(t *testing.T) {
+	c := New()
+
+	assert.Equal(t, "a", NewLazy[string](c, "a").Name())
+	assert.Equal(t, "b", NewOptionalLazy[string](c, "b").Name())
+	assert.Equal(t, "c", NewProvider[string](c, "c").Name())
+}