full unit testing and fixes

- mapToString is ordered according to setup
- setupSingle & teardownSingle no longer return "ok" states
- teardown functions support errors
- setup and teardown functions receive module

lifecycle.go

@@ -1,16 +1,13 @@
 package app
 
 import (
+	"errors"
 	"fmt"
 	"log/slog"
+	"sort"
+	"strings"
 )
 
-// setupFn is a function that runs setup logic for a module.
-type setupFn func() error
-
-// teardownFn is a function that runs teardown logic for a module.
-type teardownFn func()
-
 // LifecycleOpts contains user-exposed options when defining a lifecycle.
 type LifecycleOpts struct {
 	// DisableAutoload disables dependency autoloading (enabled by default).
@@ -25,9 +22,12 @@ type Lifecycle struct {
 	logger *slog.Logger
 
 	modules []*Module
-	setupTracker    map[string]bool
-	teardownTracker map[string]bool
 	opts    LifecycleOpts
+
+	setupCount      int
+	setupTracker    map[string]int
+	teardownCount   int
+	teardownTracker map[string]int
 }
 
 // NewLifecycle creates a new Lifecycle instance with a default logger and the
@@ -56,8 +56,8 @@ func NewLifecycleL(defaultLogger *slog.Logger, modules ...*Module) *Lifecycle {
 	return &Lifecycle{
 		logger:          defaultLogger,
 		modules:         modules,
-		setupTracker:    make(map[string]bool),
-		teardownTracker: make(map[string]bool),
+		setupTracker:    make(map[string]int),
+		teardownTracker: make(map[string]int),
 	}
 }
 
@@ -80,36 +80,37 @@ func (app *Lifecycle) Logger() *slog.Logger {
 // if dependencies are not satisfied. Lifecycle.Teardown should always be run at the end
 // of the application lifecycle to ensure all resources are cleaned up properly.
 func (app *Lifecycle) Setup() error {
-	setupCount := 0
 	for _, mod := range app.modules {
-		if ok, err := app.setupSingle(mod, app.logger); err != nil {
+		if err := app.setupSingle(mod, app.logger); err != nil {
 			return err
-		} else if ok {
-			setupCount++
 		}
 	}
 
 	app.logger.Info("Lifecycle modules initialized, backend setup complete",
-		"count", setupCount, "modules", mapToString(app.setupTracker))
+		"modules", mapToString(app.setupTracker))
 
 	return nil
 }
 
 // Teardown runs all module teardown functions in reverse order of setup.
 // Teardown should always be run at the end of the application lifecycle
-// to ensure all resources are cleaned up properly.
+// to ensure all resources are cleaned up properly. All module tear down
+// errors are returned as a single error (non-blocking).
 func (app *Lifecycle) Teardown() error {
-	teardownCount := 0
+	var err error
 	for i := len(app.modules) - 1; i >= 0; i-- {
-		if ok, err := app.singleTeardown(app.modules[i]); err != nil {
-			return err
-		} else if ok {
-			teardownCount++
+		if singleErr := app.teardownSingle(app.modules[i]); singleErr != nil {
+			err = errors.Join(err, singleErr)
 		}
 	}
 
+	if err != nil {
+		app.logger.Error("Error tearing down modules", "failures", app.setupCount-app.teardownCount, "error", err)
+		return err
+	}
+
 	app.logger.Info("All modules torn down, backend teardown complete",
-		"count", teardownCount, "modules", mapToString(app.teardownTracker))
+		"modules", mapToString(app.teardownTracker))
 
 	return nil
 }
@@ -127,6 +128,14 @@ func (app *Lifecycle) Require(modules ...*Module) error {
 // This variation is useful when you need to set up modules with a non-
 // default logger.
 func (app *Lifecycle) RequireL(logger *slog.Logger, modules ...*Module) error {
+	if logger == nil {
+		logger = app.logger
+	}
+
+	if len(modules) == 0 {
+		return fmt.Errorf("no modules to require")
+	}
+
 	for _, mod := range modules {
 		if mod == nil {
 			return fmt.Errorf("module is nil")
@@ -135,6 +144,8 @@ func (app *Lifecycle) RequireL(logger *slog.Logger, modules ...*Module) error {
 		// Check if the module is already set up
 		if _, ok := app.setupTracker[mod.name]; ok {
 			app.logger.Warn("module already set up, ignoring", "module", mod.name)
+			mod.loaded = true
+			mod.logger = logger
 			continue
 		}
 
@@ -142,7 +153,7 @@ func (app *Lifecycle) RequireL(logger *slog.Logger, modules ...*Module) error {
 		app.modules = append(app.modules, mod)
 
 		// Run the setup function for the module
-		if _, err := app.setupSingle(mod, logger); err != nil {
+		if err := app.setupSingle(mod, logger); err != nil {
 			return fmt.Errorf("error setting up required module '%s': %w", mod.name, err)
 		}
 	}
@@ -152,10 +163,11 @@ func (app *Lifecycle) RequireL(logger *slog.Logger, modules ...*Module) error {
 	return nil
 }
 
-// setupSingle is a helper function to set up a single module.
-func (app *Lifecycle) setupSingle(mod *Module, logger *slog.Logger) (bool, error) {
+// setupSingle is a helper function to set up a single module. Returns an error
+// if the module cannot be set up or if dependencies are not satisfied.
+func (app *Lifecycle) setupSingle(mod *Module, logger *slog.Logger) error {
 	if mod == nil {
-		return false, fmt.Errorf("module is nil")
+		return fmt.Errorf("module is nil")
 	}
 
 	// Set the logger for the module
@@ -165,59 +177,59 @@ func (app *Lifecycle) setupSingle(mod *Module, logger *slog.Logger) (bool, error
 	for _, dep := range mod.depends {
 		if _, ok := app.setupTracker[dep]; !ok {
 			if app.opts.DisableAutoload {
-				return false, fmt.Errorf("dependency '%s' not satisfied for '%s'", dep, mod.name)
+				return fmt.Errorf("dependency '%s' not satisfied for '%s'", dep, mod.name)
 			} else {
 				// Attempt to set up the dependency
-				mod, err := app.getModuleByName(dep)
+				depmod, err := app.getModuleByName(dep)
 				if err != nil {
-					return false, err
+					return fmt.Errorf("error getting dependency '%s' for '%s': %w", dep, mod.name, err)
 				}
 
-				if _, err := app.setupSingle(mod, logger); err != nil {
-					return false, fmt.Errorf("error setting up dependency '%s' for '%s': %w", dep, mod.name, err)
+				if err := app.setupSingle(depmod, logger); err != nil {
+					return fmt.Errorf("error setting up dependency '%s' for '%s': %w", dep, mod.name, err)
 				}
-
 			}
 		}
 	}
 
 	if mod.setup != nil {
 		// Run the setup function for the module
-		if err := mod.setup(); err != nil {
-			return false, fmt.Errorf("error initializing '%s': %w", mod.name, err)
+		if err := mod.setup(mod); err != nil {
+			return fmt.Errorf("error initializing '%s': %w", mod.name, err)
+		}
 	}
 
 	// Mark this module as setup
-		app.setupTracker[mod.name] = true
+	app.setupTracker[mod.name] = app.setupCount
+	app.setupCount++
 	mod.loaded = true
-		return true, nil
+	return nil
 }
 
-	return false, nil
-}
-
-// singleTeardown is a helper function to tear down a single module.
-func (app *Lifecycle) singleTeardown(mod *Module) (bool, error) {
+// teardownSingle is a helper function to tear down a single module. Returns
+// an error if anything goes wrong.
+func (app *Lifecycle) teardownSingle(mod *Module) error {
 	if mod == nil {
-		return false, fmt.Errorf("module is nil")
+		return fmt.Errorf("module is nil")
 	}
 
 	// Check if the module was set up
 	if _, ok := app.setupTracker[mod.name]; !ok {
-		return false, nil
+		return fmt.Errorf("module '%s' is not set up, cannot tear down", mod.name)
 	}
 
 	// Run the teardown function for the module
 	if mod.teardown != nil {
-		mod.teardown()
-
-		// Mark this module as torn down
-		app.teardownTracker[mod.name] = true
-		mod.loaded = false
-		return true, nil
+		if err := mod.teardown(mod); err != nil {
+			return fmt.Errorf("error tearing down '%s': %w", mod.name, err)
+		}
 	}
 
-	return false, nil
+	// Mark this module as torn down
+	app.teardownTracker[mod.name] = app.teardownCount
+	app.teardownCount++
+	mod.loaded = false
+	return nil
 }
 
 // getModuleByName retrieves a module by its name from the lifecycle.
@@ -227,21 +239,30 @@ func (app *Lifecycle) getModuleByName(name string) (*Module, error) {
 			return mod, nil
 		}
 	}
-	return nil, fmt.Errorf("module '%s' not found", name)
+	return nil, ErrModuleNotFound
 }
 
-// mapToString converts a map to an opinionated string representation.
-func mapToString(m map[string]bool) string {
+// mapToString converts a map to an ordered, opinionated string representation.
+func mapToString(m map[string]int) string {
 	if len(m) == 0 {
 		return "[]"
 	}
 
-	result := "["
+	// Sort the map by value
+	values := make([]int, 0, len(m))
+	reverseMap := make(map[int]string, len(m))
 	for k, v := range m {
-		if v {
-			result += fmt.Sprintf("'%s' ", k)
+		values = append(values, v)
+		reverseMap[v] = k
+	}
+	sort.Ints(values)
+
+	result := make([]string, 0, len(m))
+	for _, v := range values {
+		if name, ok := reverseMap[v]; ok {
+			result = append(result, fmt.Sprintf("'%s'", name))
 		}
 	}
-	result = result[:len(result)-1] + "]"
-	return result
+
+	return "[" + strings.Join(result, " ") + "]"
 }

lifecycle_test.go

@@ -0,0 +1,541 @@
+package app
+
+import (
+	"errors"
+	"log/slog"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewLifecycle(t *testing.T) {
+	assert := assert.New(t)
+
+	lc := NewLifecycle()
+	assert.NotNil(lc, "expected Lifecycle instance to be created")
+	assert.Equal(slog.Default(), lc.logger, "expected default logger to be set")
+}
+
+func TestNewLifecycleL(t *testing.T) {
+	assert := assert.New(t)
+
+	// Create a blank Lifecycle instance with a custom logger
+	logger := slog.Default()
+	lc := NewLifecycleL(logger)
+
+	assert.NotNil(lc)
+	assert.Equal(logger, lc.logger, "expected logger to be set")
+	assert.Len(lc.modules, 0, "expected modules to be empty")
+	assert.Len(lc.setupTracker, 0, "expected setup tracker to be empty")
+	assert.Len(lc.teardownTracker, 0, "expected teardown tracker to be empty")
+
+	// Test with modules
+	mod1 := NewModule("module1", ModuleOpts{})
+	mod2 := NewModule("module2", ModuleOpts{})
+
+	lcWithModules := NewLifecycleL(logger, mod1, mod2)
+	assert.NotNil(lcWithModules, "expected Lifecycle with modules to be created")
+	assert.Contains(lcWithModules.modules, mod1, "expected module1 to be included")
+	assert.Contains(lcWithModules.modules, mod2, "expected module2 to be included")
+	assert.Len(lcWithModules.modules, 2, "expected two modules to be present")
+
+	// Test for duplicate module names
+	assert.PanicsWithValue("duplicate module name: module1", func() {
+		NewLifecycleL(logger, mod1, mod1)
+	}, "expected panic on duplicate module names")
+}
+
+func TestLifecycle_WithOpts(t *testing.T) {
+	assert := assert.New(t)
+
+	lc := NewLifecycle()
+	opts := LifecycleOpts{
+		DisableAutoload: true,
+	}
+
+	lc.WithOpts(opts)
+	assert.Equal(opts, lc.opts, "expected Lifecycle to have the provided options")
+}
+
+func TestLifecycle_Logger(t *testing.T) {
+	assert := assert.New(t)
+
+	lc := NewLifecycle()
+	assert.Equal(slog.Default(), lc.Logger(), "expected Logger to return a logger")
+
+	// Test panic when logger is not initialized
+	lc.logger = nil
+	assert.PanicsWithValue("lifecycle logger is not initialized", func() {
+		lc.Logger()
+	}, "expected Logger to panic when logger is not set")
+}
+
+func TestLifecycle_Setup(t *testing.T) {
+	cases := []struct {
+		name        string
+		modules     []*Module
+		expectedErr string
+	}{
+		{
+			name:    "empty lifecycle",
+			modules: nil,
+		},
+		{
+			name: "single module with setup",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "multiple modules",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{}),
+				NewModule("module2", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "module with setup error",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Setup: func(m *Module) error { return errors.New("setup failed") },
+				}),
+			},
+			expectedErr: "setup failed",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			lc := NewLifecycle(tc.modules...)
+
+			err := lc.Setup()
+
+			if tc.expectedErr == "" {
+				assert.NoError(err, "expected Setup to succeed")
+				for _, mod := range tc.modules {
+					if mod.setup != nil {
+						_, ok := lc.setupTracker[mod.name]
+						assert.True(ok, "expected module to be marked as set up")
+					}
+				}
+			} else {
+				assert.Error(err, "expected Setup to fail")
+				assert.Contains(err.Error(), tc.expectedErr, "expected error message to match")
+			}
+		})
+	}
+}
+
+func TestLifecycle_Teardown(t *testing.T) {
+	cases := []struct {
+		name        string
+		modules     []*Module
+		expectedErr []string
+	}{
+		{
+			name:    "empty lifecycle",
+			modules: nil,
+		},
+		{
+			name: "single module with teardown",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Teardown: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "multiple modules",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{}),
+				NewModule("module2", ModuleOpts{
+					Teardown: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "module with teardown error",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Teardown: func(m *Module) error { return errors.New("teardown failed") },
+				}),
+			},
+			expectedErr: []string{"teardown failed"},
+		},
+		{
+			name: "multiple modules with teardown errors",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Teardown: func(m *Module) error { return errors.New("module1 teardown failed") },
+				}),
+				NewModule("module2", ModuleOpts{
+					Teardown: func(m *Module) error { return errors.New("module2 teardown failed") },
+				}),
+			},
+			expectedErr: []string{"module1 teardown failed", "module2 teardown failed"},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			lc := NewLifecycle(tc.modules...)
+
+			// Fake setup for all modules
+			for _, mod := range tc.modules {
+				lc.setupTracker[mod.name] = 0 // Mark as set up
+			}
+
+			err := lc.Teardown()
+
+			if len(tc.expectedErr) == 0 {
+				assert.NoError(err, "expected Teardown to succeed")
+				for _, mod := range tc.modules {
+					if mod.teardown != nil {
+						_, ok := lc.teardownTracker[mod.name]
+						assert.True(ok, "expected module to be marked as torn down")
+					}
+				}
+			} else {
+				assert.Error(err, "expected Teardown to fail")
+				for _, expected := range tc.expectedErr {
+					assert.Contains(err.Error(), expected, "expected error message to match")
+				}
+			}
+		})
+	}
+}
+
+func TestLifecycle_Require(t *testing.T) {
+	lc := NewLifecycle()
+	mod := NewModule("module1", ModuleOpts{
+		Setup: func(m *Module) error { return nil },
+	})
+	lc.Require(mod)
+	assert.Equal(t, lc.logger, mod.logger, "expected module logger to match lifecycle logger")
+}
+
+func TestLifecycle_RequireL(t *testing.T) {
+	cases := []struct {
+		name            string
+		logger          *slog.Logger
+		modules         []*Module
+		existingModules []*Module
+		expectedErr     string
+	}{
+		{
+			name:        "no modules",
+			expectedErr: "no modules to require",
+		},
+		{
+			name:        "nil module",
+			modules:     []*Module{nil},
+			expectedErr: "module is nil",
+		},
+		{
+			name: "basic module",
+			modules: []*Module{
+				NewModule("testModule", ModuleOpts{
+					Setup: func(m *Module) error {
+						if m.name != "testModule" {
+							return errors.New("module name mismatch")
+						}
+						return nil
+					},
+				}),
+			},
+		},
+		{
+			name: "several modules",
+			modules: []*Module{
+				NewModule("module1", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+				NewModule("module2", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "module with setup error",
+			modules: []*Module{
+				NewModule("errorModule", ModuleOpts{
+					Setup: func(m *Module) error { return errors.New("setup failed") },
+				}),
+			},
+			expectedErr: "setup failed",
+		},
+		{
+			name: "module with dependency",
+			modules: []*Module{
+				NewModule("dependentModule", ModuleOpts{
+					Setup:   func(m *Module) error { return nil },
+					Depends: []string{"dependencyModule"},
+				}),
+			},
+			existingModules: []*Module{
+				NewModule("dependencyModule", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "duplicate module names",
+			modules: []*Module{
+				NewModule("duplicateModule", ModuleOpts{}),
+				NewModule("duplicateModule", ModuleOpts{}),
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			lc := NewLifecycle(tc.existingModules...)
+
+			l := tc.logger
+			if l == nil {
+				l = lc.logger
+			}
+
+			err := lc.RequireL(tc.logger, tc.modules...)
+
+			if tc.expectedErr == "" {
+				assert.NoError(err, "expected RequireL to succeed")
+				for _, mod := range tc.modules {
+					if mod != nil {
+						_, ok := lc.setupTracker[mod.name]
+						assert.True(ok, "expected module to be marked as set up")
+						assert.True(mod.loaded, "expected module to be loaded")
+						assert.Equal(l, mod.logger, "expected module logger to match")
+					}
+				}
+			} else {
+				assert.Error(err, "expected RequireL to fail")
+				assert.Contains(err.Error(), tc.expectedErr, "expected error message to match")
+			}
+		})
+	}
+
+}
+
+func TestLifecycle_setupSingle(t *testing.T) {
+	cases := []struct {
+		name         string
+		lc           *Lifecycle
+		targetModule *Module
+		modules      []*Module
+		expectedErr  string
+		logger       *slog.Logger
+	}{
+		{
+			name:         "nil module",
+			targetModule: nil,
+			expectedErr:  "module is nil",
+		},
+		{
+			name: "basic module setup",
+			targetModule: NewModule("testModule", ModuleOpts{
+				Setup: func(m *Module) error {
+					if m.name != "testModule" {
+						return errors.New("module name mismatch")
+					}
+					return nil
+				},
+			}),
+		},
+		{
+			name: "module with dependencies",
+			targetModule: NewModule("dependentModule", ModuleOpts{
+				Setup:   func(m *Module) error { return nil },
+				Depends: []string{"dependencyModule"},
+			}),
+			modules: []*Module{
+				NewModule("dependencyModule", ModuleOpts{
+					Setup: func(m *Module) error { return nil },
+				}),
+			},
+		},
+		{
+			name: "module with missing dependency",
+			targetModule: NewModule("dependentModule", ModuleOpts{
+				Setup:   func(m *Module) error { return nil },
+				Depends: []string{"missingDependency"},
+			}),
+			expectedErr: "error getting dependency",
+		},
+		{
+			name: "module setup error",
+			targetModule: NewModule("errorModule", ModuleOpts{
+				Setup: func(m *Module) error { return errors.New("setup failed") },
+			}),
+			expectedErr: "setup failed",
+		},
+		{
+			name: "module dependency setup error",
+			targetModule: NewModule("moduleWithoutError", ModuleOpts{
+				Setup:   func(m *Module) error { return nil },
+				Depends: []string{"errorModule"},
+			}),
+			modules: []*Module{
+				NewModule("errorModule", ModuleOpts{
+					Setup: func(m *Module) error { return errors.New("dependency setup failed") },
+				}),
+			},
+			expectedErr: "error initializing 'errorModule'",
+		},
+		{
+			name: "dependency without autoload",
+			lc: NewLifecycle().WithOpts(LifecycleOpts{
+				DisableAutoload: true,
+			}),
+			targetModule: NewModule("dependentModule", ModuleOpts{
+				Setup:   func(m *Module) error { return nil },
+				Depends: []string{"dependencyModule"},
+			}),
+			expectedErr: "not satisfied",
+		},
+		{
+			name:         "module without setup function",
+			targetModule: NewModule("noSetupModule", ModuleOpts{}),
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			l := tc.logger
+			if l == nil {
+				l = slog.Default()
+			}
+
+			lc := tc.lc
+			if lc == nil {
+				lc = NewLifecycle(tc.modules...)
+			}
+
+			err := lc.setupSingle(tc.targetModule, l)
+
+			if tc.targetModule != nil {
+				assert.Equal(l, tc.targetModule.logger, "expected module logger to match")
+			}
+
+			if tc.expectedErr == "" {
+				assert.NoError(err, "expected no error from setupSingle")
+			} else {
+				assert.Contains(err.Error(), tc.expectedErr, "expected error message to match")
+			}
+		})
+	}
+
+}
+
+func TestLifecycle_teardownSingle(t *testing.T) {
+	cases := []struct {
+		name         string
+		targetModule *Module
+		modules      []string
+		expectedErr  string
+	}{
+		{
+			name:        "nil module",
+			expectedErr: "module is nil",
+		},
+		{
+			name: "basic module teardown",
+			targetModule: NewModule("testModule", ModuleOpts{
+				Teardown: func(m *Module) error {
+					if m.name != "testModule" {
+						return errors.New("module name mismatch")
+					}
+					return nil
+				},
+			}),
+			modules: []string{"testModule"},
+		},
+		{
+			name: "module not set up",
+			targetModule: NewModule("notSetUpModule", ModuleOpts{
+				Teardown: func(m *Module) error { return nil },
+			}),
+			expectedErr: "not set up, cannot tear down",
+		},
+		{
+			name:         "module without teardown function",
+			targetModule: NewModule("noTeardownModule", ModuleOpts{}),
+			modules:      []string{"noTeardownModule"},
+		},
+		{
+			name: "module with teardown error",
+			targetModule: NewModule("errorModule", ModuleOpts{
+				Teardown: func(m *Module) error { return errors.New("teardown failed") },
+			}),
+			modules:     []string{"errorModule"},
+			expectedErr: "error tearing down",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			lc := NewLifecycle()
+
+			// Fake setup for all modules
+			var setupCount int
+			for _, mod := range tc.modules {
+				lc.setupTracker[mod] = setupCount
+				setupCount++
+			}
+
+			err := lc.teardownSingle(tc.targetModule)
+
+			if tc.expectedErr == "" {
+				assert.NoError(err, "expected no error from teardownSingle")
+			} else {
+				assert.Contains(err.Error(), tc.expectedErr, "expected error message to match")
+			}
+		})
+	}
+}
+
+func Test_mapToString(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    map[string]int
+		expected string
+	}{
+		{
+			name:     "empty map",
+			input:    map[string]int{},
+			expected: "[]",
+		},
+		{
+			name:     "single entry",
+			input:    map[string]int{"key1": 0},
+			expected: "['key1']",
+		},
+		{
+			name:     "multiple entries",
+			input:    map[string]int{"key1": 0, "key2": 3, "key3": 2},
+			expected: "['key1' 'key3' 'key2']",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert := assert.New(t)
+			result := mapToString(tc.input)
+			assert.Equal(tc.expected, result, "expected mapToString to return correct string representation")
+		})
+	}
+}

module.go

@@ -1,17 +1,24 @@
 package app
 
 import (
+	"errors"
 	"fmt"
 	"log/slog"
 )
 
+// ErrModuleNotFound is returned when a module is not found in the lifecycle.
+var ErrModuleNotFound = errors.New("module not found")
+
+// moduleFn is a function type for module setup and teardown functions.
+type moduleFn func(*Module) error
+
 // Module represents a sub-system of the application, with its setup and
 // teardown functions and dependencies.
 type Module struct {
 	logger   *slog.Logger
 	name     string
-	setup    setupFn
-	teardown teardownFn
+	setup    moduleFn
+	teardown moduleFn
 	depends  []string
 	loaded   bool // loaded indicates if the module has been set up
 }
@@ -19,9 +26,9 @@ type Module struct {
 // ModuleOpts contains user-exposed options when defining a module.
 type ModuleOpts struct {
 	// Setup is the setup function for the module.
-	Setup setupFn
+	Setup moduleFn
 	// Teardown is the teardown function for the module.
-	Teardown teardownFn
+	Teardown moduleFn
 	// Depends is a list of modules that this module depends on. Each entry must
 	// be the exact name of a module registered in the lifecycle.
 	Depends []string

module_test.go

@@ -0,0 +1,61 @@
+package app
+
+import (
+	"log/slog"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewModule(t *testing.T) {
+	assert := assert.New(t)
+
+	// Test creating a module with no options
+	mod := NewModule("testModule", ModuleOpts{})
+	assert.NotNil(mod, "expected module to be created")
+	assert.Equal("testModule", mod.name, "expected module name to match")
+	assert.Nil(mod.setup, "expected setup function to be nil")
+	assert.Nil(mod.teardown, "expected teardown function to be nil")
+	assert.Empty(mod.depends, "expected dependencies to be empty")
+	assert.False(mod.loaded, "expected module to not be loaded")
+
+	// Test creating a module with setup and teardown functions and dependencies
+	setupFn := func(m *Module) error { return nil }
+	teardownFn := func(m *Module) error { return nil }
+
+	modWithOpts := NewModule("testModuleWithOpts", ModuleOpts{
+		Setup:    setupFn,
+		Teardown: teardownFn,
+		Depends:  []string{"dependency1", "dependency2"},
+	})
+	assert.NotNil(modWithOpts, "expected module with options to be created")
+	assert.NotNil(modWithOpts.setup, "expected setup function to be set")
+	assert.NotNil(modWithOpts.teardown, "expected teardown function to be set")
+	assert.Equal([]string{"dependency1", "dependency2"}, modWithOpts.depends, "expected dependencies to match")
+}
+
+func TestModule(t *testing.T) {
+	assert := assert.New(t)
+
+	// Create a module and set its logger
+	mod := NewModule("testModule", ModuleOpts{})
+	assert.Panics(func() { mod.Logger() }, "expected Logger to panic when logger is not set")
+	logger := slog.Default()
+	mod.logger = logger
+
+	// Test Logger method
+	assert.Equal(logger, mod.Logger(), "expected Logger to return the correct logger")
+
+	// Test Name method
+	assert.Equal("testModule", mod.Name(), "expected Name to return the module's name")
+
+	// Test Loaded method
+	assert.False(mod.Loaded(), "expected Loaded to return false initially")
+
+	// Test RequireLoaded method
+	assert.Panics(func() { mod.RequireLoaded() }, "expected RequireLoaded to panic when module is not loaded")
+
+	// Test setting the module as loaded
+	mod.loaded = true
+	assert.NotPanics(func() { mod.RequireLoaded() }, "expected RequireLoaded to not panic when module is loaded")
+}