Refactor tests to get full coverage

Test coverage goes from 75.6% to 100%

Makefile

@@ -32,7 +32,7 @@ vet: ## Run go vet linter
 
 test-cover-html: ## Generate test coverage report
 	go test -coverprofile=coverage.out -covermode=count
-	go tool cover -func=coverage-all.out
+	go tool cover -func=coverage.out
 
 help:
 	@grep -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'

cast_test.go

@@ -6,6 +6,7 @@
 package cast
 
 import (
+	"fmt"
 	"html/template"
 	"testing"
 	"time"
@@ -13,83 +14,283 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestToInt(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToInt(8), 8)
-	assert.Equal(t, ToInt(8.31), 8)
-	assert.Equal(t, ToInt("8"), 8)
-	assert.Equal(t, ToInt(true), 1)
-	assert.Equal(t, ToInt(false), 0)
-	assert.Equal(t, ToInt(eight), 8)
+func TestToIntE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect int
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float64(8.31), 8, false},
+		{true, 1, false},
+		{false, 0, false},
+		{"8", 8, false},
+		{nil, 0, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToIntE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToInt(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToInt64(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToInt64(int64(8)), int64(8))
-	assert.Equal(t, ToInt64(8), int64(8))
-	assert.Equal(t, ToInt64(8.31), int64(8))
-	assert.Equal(t, ToInt64("8"), int64(8))
-	assert.Equal(t, ToInt64(true), int64(1))
-	assert.Equal(t, ToInt64(false), int64(0))
-	assert.Equal(t, ToInt64(eight), int64(8))
+func TestToInt64E(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect int64
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float64(8.31), 8, false},
+		{true, 1, false},
+		{false, 0, false},
+		{"8", 8, false},
+		{nil, 0, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToInt64E(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToInt64(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToInt32(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToInt32(int32(8)), int32(8))
-	assert.Equal(t, ToInt32(8), int32(8))
-	assert.Equal(t, ToInt32(8.31), int32(8))
-	assert.Equal(t, ToInt32("8"), int32(8))
-	assert.Equal(t, ToInt32(true), int32(1))
-	assert.Equal(t, ToInt32(false), int32(0))
-	assert.Equal(t, ToInt32(eight), int32(8))
+func TestToInt32E(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect int32
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float64(8.31), 8, false},
+		{true, 1, false},
+		{false, 0, false},
+		{"8", 8, false},
+		{nil, 0, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToInt32E(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToInt32(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToInt16(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToInt16(int16(8)), int16(8))
-	assert.Equal(t, ToInt16(8), int16(8))
-	assert.Equal(t, ToInt16(8.31), int16(8))
-	assert.Equal(t, ToInt16("8"), int16(8))
-	assert.Equal(t, ToInt16(true), int16(1))
-	assert.Equal(t, ToInt16(false), int16(0))
-	assert.Equal(t, ToInt16(eight), int16(8))
+func TestToInt16E(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect int16
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float64(8.31), 8, false},
+		{true, 1, false},
+		{false, 0, false},
+		{"8", 8, false},
+		{nil, 0, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToInt16E(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToInt16(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToInt8(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToInt8(int8(8)), int8(8))
-	assert.Equal(t, ToInt8(8), int8(8))
-	assert.Equal(t, ToInt8(8.31), int8(8))
-	assert.Equal(t, ToInt8("8"), int8(8))
-	assert.Equal(t, ToInt8(true), int8(1))
-	assert.Equal(t, ToInt8(false), int8(0))
-	assert.Equal(t, ToInt8(eight), int8(8))
+func TestToInt8E(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect int8
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float64(8.31), 8, false},
+		{true, 1, false},
+		{false, 0, false},
+		{"8", 8, false},
+		{nil, 0, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToInt8E(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToInt8(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToFloat64(t *testing.T) {
-	var eight interface{} = 8
-	assert.Equal(t, ToFloat64(8), 8.00)
-	assert.Equal(t, ToFloat64(8.31), 8.31)
-	assert.Equal(t, ToFloat64("8.31"), 8.31)
-	assert.Equal(t, ToFloat64(eight), 8.0)
+func TestToFloat64E(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect float64
+		iserr  bool
+	}{
+		{int(8), 8, false},
+		{int8(8), 8, false},
+		{int16(8), 8, false},
+		{int32(8), 8, false},
+		{int64(8), 8, false},
+		{float32(8), 8, false},
+		{float64(8.31), 8.31, false},
+		{"8", 8, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToFloat64E(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToFloat64(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToString(t *testing.T) {
-	var foo interface{} = "one more time"
-	assert.Equal(t, ToString(8), "8")
-	assert.Equal(t, ToString(int64(16)), "16")
-	assert.Equal(t, ToString(8.12), "8.12")
-	assert.Equal(t, ToString([]byte("one time")), "one time")
-	assert.Equal(t, ToString(template.HTML("one time")), "one time")
-	assert.Equal(t, ToString(template.URL("http://somehost.foo")), "http://somehost.foo")
-	assert.Equal(t, ToString(template.JS("(1+2)")), "(1+2)")
-	assert.Equal(t, ToString(template.CSS("a")), "a")
-	assert.Equal(t, ToString(template.HTMLAttr("a")), "a")
-	assert.Equal(t, ToString(foo), "one more time")
-	assert.Equal(t, ToString(nil), "")
-	assert.Equal(t, ToString(true), "true")
-	assert.Equal(t, ToString(false), "false")
+func TestToStringE(t *testing.T) {
+	type Key struct {
+		k string
+	}
+	key := &Key{"foo"}
+
+	tests := []struct {
+		input  interface{}
+		expect string
+		iserr  bool
+	}{
+		{int(8), "8", false},
+		{int64(8), "8", false},
+		{float64(8.31), "8.31", false},
+		{true, "true", false},
+		{false, "false", false},
+		{nil, "", false},
+		{[]byte("one time"), "one time", false},
+		{"one more time", "one more time", false},
+		{template.HTML("one time"), "one time", false},
+		{template.URL("http://somehost.foo"), "http://somehost.foo", false},
+		{template.JS("(1+2)"), "(1+2)", false},
+		{template.CSS("a"), "a", false},
+		{template.HTMLAttr("a"), "a", false},
+		// errors
+		{testing.T{}, "", true},
+		{key, "", true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToString(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
 type foo struct {
@@ -101,7 +302,6 @@ func (x foo) String() string {
 }
 
 func TestStringerToString(t *testing.T) {
-
 	var x foo
 	x.val = "bar"
 	assert.Equal(t, "bar", ToString(x))
@@ -121,10 +321,7 @@ func TestErrorToString(t *testing.T) {
 	assert.Equal(t, "bar", ToString(x))
 }
 
-func TestMaps(t *testing.T) {
-	var taxonomies = map[interface{}]interface{}{"tag": "tags", "group": "groups"}
-	var stringMapBool = map[interface{}]interface{}{"v1": true, "v2": false}
-
+func TestStringMapStringSliceE(t *testing.T) {
 	// ToStringMapString inputs/outputs
 	var stringMapString = map[string]string{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
 	var stringMapInterface = map[string]interface{}{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
@@ -134,6 +331,7 @@ func TestMaps(t *testing.T) {
 	// ToStringMapStringSlice inputs/outputs
 	var stringMapStringSlice = map[string][]string{"key 1": {"value 1", "value 2", "value 3"}, "key 2": {"value 1", "value 2", "value 3"}, "key 3": {"value 1", "value 2", "value 3"}}
 	var stringMapInterfaceSlice = map[string][]interface{}{"key 1": {"value 1", "value 2", "value 3"}, "key 2": {"value 1", "value 2", "value 3"}, "key 3": {"value 1", "value 2", "value 3"}}
+	var stringMapInterfaceInterfaceSlice = map[string]interface{}{"key 1": []interface{}{"value 1", "value 2", "value 3"}, "key 2": []interface{}{"value 1", "value 2", "value 3"}, "key 3": []interface{}{"value 1", "value 2", "value 3"}}
 	var stringMapStringSingleSliceFieldsResult = map[string][]string{"key 1": {"value", "1"}, "key 2": {"value", "2"}, "key 3": {"value", "3"}}
 	var interfaceMapStringSlice = map[interface{}][]string{"key 1": {"value 1", "value 2", "value 3"}, "key 2": {"value 1", "value 2", "value 3"}, "key 3": {"value 1", "value 2", "value 3"}}
 	var interfaceMapInterfaceSlice = map[interface{}][]interface{}{"key 1": {"value 1", "value 2", "value 3"}, "key 2": {"value 1", "value 2", "value 3"}, "key 3": {"value 1", "value 2", "value 3"}}
@@ -144,61 +342,329 @@ func TestMaps(t *testing.T) {
 	var stringMapInterface1 = map[string]interface{}{"key 1": []string{"value 1"}, "key 2": []string{"value 2"}}
 	var stringMapInterfaceResult1 = map[string][]string{"key 1": {"value 1"}, "key 2": {"value 2"}}
 
-	assert.Equal(t, ToStringMap(taxonomies), map[string]interface{}{"tag": "tags", "group": "groups"})
-	assert.Equal(t, ToStringMapBool(stringMapBool), map[string]bool{"v1": true, "v2": false})
-
-	// ToStringMapString tests
-	assert.Equal(t, ToStringMapString(stringMapString), stringMapString)
-	assert.Equal(t, ToStringMapString(stringMapInterface), stringMapString)
-	assert.Equal(t, ToStringMapString(interfaceMapString), stringMapString)
-	assert.Equal(t, ToStringMapString(interfaceMapInterface), stringMapString)
-
-	// ToStringMapStringSlice tests
-	assert.Equal(t, ToStringMapStringSlice(stringMapStringSlice), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(stringMapInterfaceSlice), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(stringMapStringSliceMultiple), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(stringMapStringSliceMultiple), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(stringMapString), stringMapStringSliceSingle)
-	assert.Equal(t, ToStringMapStringSlice(stringMapInterface), stringMapStringSliceSingle)
-	assert.Equal(t, ToStringMapStringSlice(interfaceMapStringSlice), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(interfaceMapInterfaceSlice), stringMapStringSlice)
-	assert.Equal(t, ToStringMapStringSlice(interfaceMapString), stringMapStringSingleSliceFieldsResult)
-	assert.Equal(t, ToStringMapStringSlice(interfaceMapInterface), stringMapStringSingleSliceFieldsResult)
-	assert.Equal(t, ToStringMapStringSlice(stringMapInterface1), stringMapInterfaceResult1)
+	type Key struct {
+		k string
+	}
+
+	tests := []struct {
+		input  interface{}
+		expect map[string][]string
+		iserr  bool
+	}{
+		{stringMapStringSlice, stringMapStringSlice, false},
+		{stringMapInterfaceSlice, stringMapStringSlice, false},
+		{stringMapInterfaceInterfaceSlice, stringMapStringSlice, false},
+		{stringMapStringSliceMultiple, stringMapStringSlice, false},
+		{stringMapStringSliceMultiple, stringMapStringSlice, false},
+		{stringMapString, stringMapStringSliceSingle, false},
+		{stringMapInterface, stringMapStringSliceSingle, false},
+		{stringMapInterface1, stringMapInterfaceResult1, false},
+		{interfaceMapStringSlice, stringMapStringSlice, false},
+		{interfaceMapInterfaceSlice, stringMapStringSlice, false},
+		{interfaceMapString, stringMapStringSingleSliceFieldsResult, false},
+		{interfaceMapInterface, stringMapStringSingleSliceFieldsResult, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+		{map[interface{}]interface{}{"foo": testing.T{}}, nil, true},
+		{map[interface{}]interface{}{Key{"foo"}: "bar"}, nil, true}, // ToStringE(Key{"foo"}) should fail
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringMapStringSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToStringMapStringSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestSlices(t *testing.T) {
-	assert.Equal(t, []string{"a", "b"}, ToStringSlice([]string{"a", "b"}))
-	assert.Equal(t, []string{"1", "3"}, ToStringSlice([]interface{}{1, 3}))
-	assert.Equal(t, []int{1, 3}, ToIntSlice([]int{1, 3}))
-	assert.Equal(t, []int{1, 3}, ToIntSlice([]interface{}{1.2, 3.2}))
-	assert.Equal(t, []int{2, 3}, ToIntSlice([]string{"2", "3"}))
-	assert.Equal(t, []int{2, 3}, ToIntSlice([2]string{"2", "3"}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]bool{true, false, true}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]interface{}{true, false, true}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]int{1, 0, 1}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]string{"true", "false", "true"}))
+func TestToStringMapE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect map[string]interface{}
+		iserr  bool
+	}{
+		{map[interface{}]interface{}{"tag": "tags", "group": "groups"}, map[string]interface{}{"tag": "tags", "group": "groups"}, false},
+		{map[string]interface{}{"tag": "tags", "group": "groups"}, map[string]interface{}{"tag": "tags", "group": "groups"}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringMapE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToStringMap(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
-func TestToBool(t *testing.T) {
-	assert.Equal(t, ToBool(0), false)
-	assert.Equal(t, ToBool(nil), false)
-	assert.Equal(t, ToBool("false"), false)
-	assert.Equal(t, ToBool("FALSE"), false)
-	assert.Equal(t, ToBool("False"), false)
-	assert.Equal(t, ToBool("f"), false)
-	assert.Equal(t, ToBool("F"), false)
-	assert.Equal(t, ToBool(false), false)
-	assert.Equal(t, ToBool("foo"), false)
-
-	assert.Equal(t, ToBool("true"), true)
-	assert.Equal(t, ToBool("TRUE"), true)
-	assert.Equal(t, ToBool("True"), true)
-	assert.Equal(t, ToBool("t"), true)
-	assert.Equal(t, ToBool("T"), true)
-	assert.Equal(t, ToBool(1), true)
-	assert.Equal(t, ToBool(true), true)
-	assert.Equal(t, ToBool(-1), true)
+func TestToStringMapBoolE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect map[string]bool
+		iserr  bool
+	}{
+		{map[interface{}]interface{}{"v1": true, "v2": false}, map[string]bool{"v1": true, "v2": false}, false},
+		{map[string]interface{}{"v1": true, "v2": false}, map[string]bool{"v1": true, "v2": false}, false},
+		{map[string]bool{"v1": true, "v2": false}, map[string]bool{"v1": true, "v2": false}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringMapBoolE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToStringMapBool(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToStringMapStringE(t *testing.T) {
+	var stringMapString = map[string]string{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
+	var stringMapInterface = map[string]interface{}{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
+	var interfaceMapString = map[interface{}]string{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
+	var interfaceMapInterface = map[interface{}]interface{}{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
+
+	tests := []struct {
+		input  interface{}
+		expect map[string]string
+		iserr  bool
+	}{
+		{stringMapString, stringMapString, false},
+		{stringMapInterface, stringMapString, false},
+		{interfaceMapString, stringMapString, false},
+		{interfaceMapInterface, stringMapString, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringMapStringE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToStringMapString(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToBoolSliceE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect []bool
+		iserr  bool
+	}{
+		{[]bool{true, false, true}, []bool{true, false, true}, false},
+		{[]interface{}{true, false, true}, []bool{true, false, true}, false},
+		{[]int{1, 0, 1}, []bool{true, false, true}, false},
+		{[]string{"true", "false", "true"}, []bool{true, false, true}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+		{[]string{"foo", "bar"}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToBoolSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToBoolSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToIntSliceE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect []int
+		iserr  bool
+	}{
+		{[]int{1, 3}, []int{1, 3}, false},
+		{[]interface{}{1.2, 3.2}, []int{1, 3}, false},
+		{[]string{"2", "3"}, []int{2, 3}, false},
+		{[2]string{"2", "3"}, []int{2, 3}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+		{[]string{"foo", "bar"}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToIntSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToIntSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToSliceE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect []interface{}
+		iserr  bool
+	}{
+		{[]interface{}{1, 3}, []interface{}{1, 3}, false},
+		{[]map[string]interface{}{{"k1": 1}, {"k2": 2}}, []interface{}{map[string]interface{}{"k1": 1}, map[string]interface{}{"k2": 2}}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToStringSliceE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect []string
+		iserr  bool
+	}{
+		{[]string{"a", "b"}, []string{"a", "b"}, false},
+		{[]interface{}{1, 3}, []string{"1", "3"}, false},
+		{interface{}(1), []string{"1"}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToStringSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToStringSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
+func TestToBoolE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect bool
+		iserr  bool
+	}{
+		{0, false, false},
+		{nil, false, false},
+		{"false", false, false},
+		{"FALSE", false, false},
+		{"False", false, false},
+		{"f", false, false},
+		{"F", false, false},
+		{false, false, false},
+
+		{"true", true, false},
+		{"TRUE", true, false},
+		{"True", true, false},
+		{"t", true, false},
+		{"T", true, false},
+		{1, true, false},
+		{true, true, false},
+		{-1, true, false},
+
+		// errors
+		{"test", false, true},
+		{testing.T{}, false, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToBoolE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToBool(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
 }
 
 func BenchmarkTooBool(b *testing.B) {
@@ -218,69 +684,104 @@ func TestIndirectPointers(t *testing.T) {
 	assert.Equal(t, ToInt(z), 13)
 }
 
-func TestToTimeE(t *testing.T) {
-	cases := []struct {
-		input interface{}
-		want  time.Time
+func TestToTimeEE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect time.Time
+		iserr  bool
 	}{
-		{"2009-11-10 23:00:00 +0000 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},   // Time.String()
-		{"Tue Nov 10 23:00:00 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},        // ANSIC
-		{"Tue Nov 10 23:00:00 UTC 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},    // UnixDate
-		{"Tue Nov 10 23:00:00 +0000 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},  // RubyDate
-		{"10 Nov 09 23:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},             // RFC822
-		{"10 Nov 09 23:00 +0000", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},           // RFC822Z
-		{"Tuesday, 10-Nov-09 23:00:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)}, // RFC850
-		{"Tue, 10 Nov 2009 23:00:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},   // RFC1123
-		{"Tue, 10 Nov 2009 23:00:00 +0000", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)}, // RFC1123Z
-		{"2009-11-10T23:00:00Z", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},            // RFC3339
-		{"2009-11-10T23:00:00Z", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC)},            // RFC3339Nano
-		{"11:00PM", time.Date(0, 1, 1, 23, 0, 0, 0, time.UTC)},                              // Kitchen
-		{"Nov 10 23:00:00", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC)},                    // Stamp
-		{"Nov 10 23:00:00.000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC)},                // StampMilli
-		{"Nov 10 23:00:00.000000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC)},             // StampMicro
-		{"Nov 10 23:00:00.000000000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC)},          // StampNano
-		{"2016-03-06 15:28:01-00:00", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC)},        // RFC3339 without T
-		{"2016-03-06 15:28:01", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC)},
-		{"2016-03-06 15:28:01 -0000", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC)},
-		{"2016-03-06 15:28:01 -00:00", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC)},
-		{"2006-01-02", time.Date(2006, 1, 2, 0, 0, 0, 0, time.UTC)},
-		{"02 Jan 2006", time.Date(2006, 1, 2, 0, 0, 0, 0, time.UTC)},
-		{1472574600, time.Date(2016, 8, 30, 16, 30, 0, 0, time.UTC)},
-		{int(1482597504), time.Date(2016, 12, 24, 16, 38, 24, 0, time.UTC)},
-		{int32(1234567890), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC)},
-	}
-
-	for _, c := range cases {
-		v, err := ToTimeE(c.input)
-		assert.NoError(t, err)
-		assert.Equal(t, v.UTC(), c.want)
+		{"2009-11-10 23:00:00 +0000 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},   // Time.String()
+		{"Tue Nov 10 23:00:00 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},        // ANSIC
+		{"Tue Nov 10 23:00:00 UTC 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},    // UnixDate
+		{"Tue Nov 10 23:00:00 +0000 2009", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},  // RubyDate
+		{"10 Nov 09 23:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},             // RFC822
+		{"10 Nov 09 23:00 +0000", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},           // RFC822Z
+		{"Tuesday, 10-Nov-09 23:00:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false}, // RFC850
+		{"Tue, 10 Nov 2009 23:00:00 UTC", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},   // RFC1123
+		{"Tue, 10 Nov 2009 23:00:00 +0000", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false}, // RFC1123Z
+		{"2009-11-10T23:00:00Z", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},            // RFC3339
+		{"2009-11-10T23:00:00Z", time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC), false},            // RFC3339Nano
+		{"11:00PM", time.Date(0, 1, 1, 23, 0, 0, 0, time.UTC), false},                              // Kitchen
+		{"Nov 10 23:00:00", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC), false},                    // Stamp
+		{"Nov 10 23:00:00.000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC), false},                // StampMilli
+		{"Nov 10 23:00:00.000000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC), false},             // StampMicro
+		{"Nov 10 23:00:00.000000000", time.Date(0, 11, 10, 23, 0, 0, 0, time.UTC), false},          // StampNano
+		{"2016-03-06 15:28:01-00:00", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC), false},        // RFC3339 without T
+		{"2016-03-06 15:28:01", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC), false},
+		{"2016-03-06 15:28:01 -0000", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC), false},
+		{"2016-03-06 15:28:01 -00:00", time.Date(2016, 3, 6, 15, 28, 1, 0, time.UTC), false},
+		{"2006-01-02", time.Date(2006, 1, 2, 0, 0, 0, 0, time.UTC), false},
+		{"02 Jan 2006", time.Date(2006, 1, 2, 0, 0, 0, 0, time.UTC), false},
+		{1472574600, time.Date(2016, 8, 30, 16, 30, 0, 0, time.UTC), false},
+		{int(1482597504), time.Date(2016, 12, 24, 16, 38, 24, 0, time.UTC), false},
+		{int64(1234567890), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), false},
+		{int32(1234567890), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), false},
+		{time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), false},
+		// errors
+		{"2006", time.Time{}, true},
+		{testing.T{}, time.Time{}, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToTimeE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v.UTC(), errmsg)
+
+		// Non-E test
+		v = ToTime(test.input)
+		assert.Equal(t, test.expect, v.UTC(), errmsg)
 	}
 }
 
-func TestToDuration(t *testing.T) {
+func TestToDurationE(t *testing.T) {
 	var td time.Duration = 5
+
 	tests := []struct {
-		input    interface{}
-		expected time.Duration
+		input  interface{}
+		expect time.Duration
+		iserr  bool
 	}{
-		{time.Duration(5), td},
-		{int64(5), td},
-		{int32(5), td},
-		{int16(5), td},
-		{int8(5), td},
-		{int(5), td},
-		{float64(5), td},
-		{float32(5), td},
-		{string("5"), td},
-		{string("5ns"), td},
-		{string("5us"), time.Microsecond * td},
-		{string("5µs"), time.Microsecond * td},
-		{string("5ms"), time.Millisecond * td},
-		{string("5s"), time.Second * td},
-		{string("5m"), time.Minute * td},
-		{string("5h"), time.Hour * td},
-	}
-	for _, v := range tests {
-		assert.Equal(t, v.expected, ToDuration(v.input))
+		{time.Duration(5), td, false},
+		{int(5), td, false},
+		{int64(5), td, false},
+		{int32(5), td, false},
+		{int16(5), td, false},
+		{int8(5), td, false},
+		{float64(5), td, false},
+		{string("5"), td, false},
+		{string("5ns"), td, false},
+		{string("5us"), time.Microsecond * td, false},
+		{string("5µs"), time.Microsecond * td, false},
+		{string("5ms"), time.Millisecond * td, false},
+		{string("5s"), time.Second * td, false},
+		{string("5m"), time.Minute * td, false},
+		{string("5h"), time.Hour * td, false},
+		// errors
+		{"test", 0, true},
+		{testing.T{}, 0, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToDurationE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToDuration(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
 	}
 }