# tx · Rell standard library · Chromia Docs (concept)

> type tx A test transaction builder; i.e. a builder for test
transactions that comprise blockchain blocks. A test transaction consists of a list of test ope

Source: https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/

TYPE

# tx

```signature
type tx
```

A test transaction builder; i.e. a [builder](https://en.wikipedia.org/wiki/Builder_pattern) for test
transactions that comprise blockchain blocks.

A test transaction consists of a list of test operation calls, and a list of signing keypairs. The
test transaction builder type has functions that facilitate straightforward transaction
construction by passing operations and keys in various formats.

**See Also**

1. [Builder pattern - Wikipedia](https://en.wikipedia.org/wiki/Builder_pattern)
2. [`rell.test.op` - Rell Standard Library](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/op/)
3. [`rell.test.keypair` - Rell Standard Library](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/keypair/)

Since 0.10.4

## Methods

[copy](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/copy/)
:   Copy this transaction builder.

[nop](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/nop/)
:   Add a nop test operation call to this transaction builder.

[op](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/op/)
:   Add a list of test operation calls to this test transaction builder.

[run](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/run/)
:   Build a test block containing only this test transaction.

[run\_must\_fail](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/run_must_fail/)
:   Build a test block containing only this test transaction, asserting that the building fails

[sign](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/sign/)
:   Add the given list of keypairs as signers of this test transaction builder.

[tx](https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/rell.test/tx/tx/)

[View this page on docs.chromia.com](https://docs.chromia.com/pages/rell-stdlib/-rell%20-system%20-library/rell.test/tx/index.html)Generated API reference, mirrored from the live docs