diff --git a/backend/backend.go b/backend/backend.go
new file mode 100644
index 0000000..334ad9f
--- /dev/null
+++ b/backend/backend.go
@@ -0,0 +1,25 @@
+package backend
+
+import "github.com/Trapesys/go-ibft/proto"
+
+// Backend defines an interface all backend implementations
+// need to implement
+type Backend interface {
+	// IsValidBlock checks if the proposed block is child of parent
+	IsValidBlock(block []byte) bool
+
+	// IsValidMessage checks if signature is from sender
+	IsValidMessage(msg *proto.Message) bool
+
+	// IsProposer checks if the passed in ID is the Proposer for current view (sequence, round)
+	IsProposer(id []byte, sequence, round uint64) bool
+
+	// BuildProposal builds a new block proposal
+	BuildProposal(blockNumber uint64) ([]byte, error)
+
+	// VerifyProposalHash checks if the hash matches the proposal
+	VerifyProposalHash(proposal, hash []byte) error
+
+	// IsValidCommittedSeal checks if the seal for the proposal is valid
+	IsValidCommittedSeal(proposal, seal []byte) bool
+}
diff --git a/backend/testing.go b/backend/testing.go
new file mode 100644
index 0000000..21cff78
--- /dev/null
+++ b/backend/testing.go
@@ -0,0 +1,93 @@
+package backend
+
+import "github.com/Trapesys/go-ibft/proto"
+
+// Define delegation methods for hooks
+type isValidBlockDelegate func([]byte) bool
+type isValidMessageDelegate func(*proto.Message) bool
+type isProposerDelegate func([]byte, uint64, uint64) bool
+type buildProposalDelegate func(uint64) ([]byte, error)
+type verifyProposalHashDelegate func([]byte, []byte) error
+type isValidCommittedSealDelegate func([]byte, []byte) bool
+
+// MockBackend is the mock backend structure that is configurable
+type MockBackend struct {
+	isValidBlockFn         isValidBlockDelegate
+	isValidMessageFn       isValidMessageDelegate
+	isProposerFn           isProposerDelegate
+	buildProposalFn        buildProposalDelegate
+	verifyProposalHashFn   verifyProposalHashDelegate
+	isValidCommittedSealFn isValidCommittedSealDelegate
+}
+
+func (m *MockBackend) IsValidBlock(block []byte) bool {
+	if m.isValidBlockFn != nil {
+		return m.isValidBlockFn(block)
+	}
+
+	return true
+}
+
+func (m *MockBackend) HookIsValidBlock(fn isValidBlockDelegate) {
+	m.isValidBlockFn = fn
+}
+
+func (m *MockBackend) IsValidMessage(msg *proto.Message) bool {
+	if m.isValidBlockFn != nil {
+		return m.isValidMessageFn(msg)
+	}
+
+	return true
+}
+
+func (m *MockBackend) HookIsValidMessage(fn isValidMessageDelegate) {
+	m.isValidMessageFn = fn
+}
+
+func (m *MockBackend) IsProposer(id []byte, sequence, round uint64) bool {
+	if m.isProposerFn != nil {
+		return m.isProposerFn(id, sequence, round)
+	}
+
+	return false
+}
+
+func (m *MockBackend) HookIsProposer(fn isProposerDelegate) {
+	m.isProposerFn = fn
+}
+
+func (m *MockBackend) BuildProposal(blockNumber uint64) ([]byte, error) {
+	if m.buildProposalFn != nil {
+		return m.buildProposalFn(blockNumber)
+	}
+
+	return nil, nil
+}
+
+func (m *MockBackend) HookBuildProposal(fn buildProposalDelegate) {
+	m.buildProposalFn = fn
+}
+
+func (m *MockBackend) VerifyProposalHash(proposal, hash []byte) error {
+	if m.verifyProposalHashFn != nil {
+		return m.verifyProposalHashFn(proposal, hash)
+	}
+
+	return nil
+}
+
+func (m *MockBackend) HookVerifyProposalHash(fn verifyProposalHashDelegate) {
+	m.verifyProposalHashFn = fn
+}
+
+func (m *MockBackend) IsValidCommittedSeal(proposal, seal []byte) bool {
+	if m.isValidCommittedSealFn != nil {
+		return m.isValidCommittedSealFn(proposal, seal)
+	}
+
+	return true
+}
+
+func (m *MockBackend) HookIsValidCommittedSeal(fn isValidCommittedSealDelegate) {
+	m.isValidCommittedSealFn = fn
+}