`All()` combines the outputs of multiple `SchemaValidateFunc`, to reduce the usage of custom validation functions that implement standard validation functions.
Example provider usage:
```go
ValidateFunc: validation.All(
StringLenBetween(5, 42),
StringMatch(regexp.MustCompile(`[a-zA-Z0-9]+`), "value must be alphanumeric"),
),
```
`IntInSlice()` is the `int` equivalent of `StringInSlice()`
Example provider usage:
```go
ValidateFunc: validation.IntInSlice([]int{30, 60, 120})
```
Output from unit testing:
```
$ make test TEST=./helper/validation
==> Checking that code complies with gofmt requirements...
go generate ./...
2018/10/17 14:16:03 Generated command/internal_plugin_list.go
go list ./helper/validation | xargs -t -n4 go test -timeout=2m -parallel=4
go test -timeout=2m -parallel=4 github.com/hashicorp/terraform/helper/validation
ok github.com/hashicorp/terraform/helper/validation 1.106s
```
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