Test Shell for Interactive Environments
=========================================

This document describes how to use the `TestShell` submodule in the functional
test suite.

The `TestShell` submodule extends the `BitcoinTestFramework` functionality to
external interactive environments for prototyping and educational purposes. Just
like `BitcoinTestFramework`, the `TestShell` allows the user to:

* Manage regtest bitcoind subprocesses.
* Access RPC interfaces of the underlying bitcoind instances.
* Log events to the functional test logging utility.

The `TestShell` can be useful in interactive environments where it is necessary
to extend the object lifetime of the underlying `BitcoinTestFramework` between
user inputs. Such environments include the Python3 command line interpreter or
[Jupyter](https://jupyter.org/) notebooks running a Python3 kernel.

## 1. Requirements

* Python3
* `bitcoind` built in the same repository as the `TestShell`.

## 2. Importing `TestShell` from the Bitcoin Core repository

We can import the `TestShell` by adding the path of the configured Bitcoin Core
`test_framework` module to the beginning of the PATH variable, and then
importing the `TestShell` class from the `test_shell` sub-package. Since
the build system creates a copy of the `test_framework` module into a new `build/`
directory along with the required configuration file, the path to the build copy
must be used.

```
>>> import sys
>>> sys.path.insert(0, "/path/to/bitcoin/build/test/functional")
>>> from test_framework.test_shell import TestShell
```

The following `TestShell` methods manage the lifetime of the underlying bitcoind
processes and logging utilities.

* `TestShell().setup()`
* `TestShell().shutdown()`

The `TestShell` inherits all `BitcoinTestFramework` members and methods, such
as:
* `TestShell().nodes[index].rpc_method()`
* `TestShell().log.info("Custom log message")`

The following sections demonstrate how to initialize, run, and shut down a
`TestShell` object.

## 3. Initializing a `TestShell` object

```
>>> test = TestShell().setup(num_nodes=2, setup_clean_chain=True)
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Initializing test directory /path/to/bitcoin_func_test_XXXXXXX
```
The `TestShell` forwards all functional test parameters of the parent
`BitcoinTestFramework` object. The full set of argument keywords which can be
used to initialize the `TestShell` can be found in [section
#6](#custom-testshell-parameters) of this document.

**Note: Running multiple instances of `TestShell` is not allowed.** Running a
single process also ensures that logging remains consolidated in the same
temporary folder. If you need more bitcoind nodes than set by default (1),
simply increase the `num_nodes` parameter during setup.

```
>>> test2 = TestShell().setup()
TestShell is already running!
```

## 4. Interacting with the `TestShell`

Unlike the `BitcoinTestFramework` class, the `TestShell` keeps the underlying
Bitcoind subprocesses (nodes) and logging utilities running until the user
explicitly shuts down the `TestShell` object.

During the time between the `setup` and `shutdown` calls, all `bitcoind` node
processes and `BitcoinTestFramework` convenience methods can be accessed
interactively.

**Example: Mining a regtest chain**

By default, the `TestShell` nodes are initialized with a clean chain. This means
that each node of the `TestShell` is initialized with a block height of 0.

```
>>> test.nodes[0].getblockchaininfo()["blocks"]
0
```

We now let the first node generate 101 regtest blocks, and direct the coinbase
rewards to a wallet address owned by the mining node.

```
>>> test.nodes[0].createwallet('default')
{'name': 'default'}
>>> address = test.nodes[0].getnewaddress()
>>> test.generatetoaddress(test.nodes[0], 101, address)
['2b98dd0044aae6f1cca7f88a0acf366a4bfe053c7f7b00da3c0d115f03d67efb', ...
```
Since the two nodes are both initialized by default to establish an outbound
connection to each other during `setup`, the second node's chain will include
the mined blocks as soon as they propagate.

```
>>> test.nodes[1].getblockchaininfo()["blocks"]
101
```
The block rewards from the first block are now spendable by the wallet of the
first node.

```
>>> test.nodes[0].getbalance()
Decimal('50.00000000')
```

We can also log custom events to the logger.

```
>>> test.nodes[0].log.info("Successfully mined regtest chain!")
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework.node0 (INFO): Successfully mined regtest chain!
```

**Note: Please also consider the functional test
[readme](/test/functional/README.md), which provides an overview of the
test-framework**. Modules such as
[key.py](/test/functional/test_framework/key.py),
[script.py](/test/functional/test_framework/script.py) and
[messages.py](/test/functional/test_framework/messages.py) are particularly
useful in constructing objects which can be passed to the bitcoind nodes managed
by a running `TestShell` object.

## 5. Shutting the `TestShell` down

Shutting down the `TestShell` will safely tear down all running bitcoind
instances and remove all temporary data and logging directories.

```
>>> test.shutdown()
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Stopping nodes
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Cleaning up /path/to/bitcoin_func_test_XXXXXXX on exit
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Tests successful
```
To prevent the logs from being removed after a shutdown, simply set the
`TestShell().options.nocleanup` member to `True`.
```
>>> test.options.nocleanup = True
>>> test.shutdown()
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Stopping nodes
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Not cleaning up dir /path/to/bitcoin_func_test_XXXXXXX on exit
20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Tests successful
```

The following utility consolidates logs from the bitcoind nodes and the
underlying `BitcoinTestFramework`:

* `/path/to/bitcoin/build/test/functional/combine_logs.py
  '/path/to/bitcoin_func_test_XXXXXXX'`

## 6. Custom `TestShell` parameters

The `TestShell` object initializes with the default settings inherited from the
`BitcoinTestFramework` class. The user can override these in
`TestShell().setup(key=value)`.

**Note:** `TestShell().reset()` will reset test parameters to default values and
can be called after the TestShell is shut down.

| Test parameter key | Default Value | Description |
|---|---|---|
| `bind_to_localhost_only` | `True` | Binds bitcoind P2P services to `127.0.0.1` if set to `True`.|
| `cachedir` | `"/path/to/bitcoin/build/test/cache"` | Sets the bitcoind datadir directory. |
| `chain`  | `"regtest"` | Sets the chain-type for the underlying test bitcoind processes. |
| `configfile` | `"/path/to/bitcoin/build/test/config.ini"` | Sets the location of the test framework config file. |
| `coveragedir` | `None` | Records bitcoind RPC test coverage into this directory if set. |
| `loglevel` | `INFO` | Logs events at this level and higher. Can be set to `DEBUG`, `INFO`, `WARNING`, `ERROR` or `CRITICAL`. |
| `nocleanup` | `False` | Cleans up temporary test directory if set to `True` during `shutdown`. |
| `num_nodes` | `1` | Sets the number of initialized bitcoind processes. |
| `perf` | False | Profiles running nodes with `perf` for the duration of the test if set to `True`. |
| `rpc_timeout` | `60` | Sets the RPC server timeout for the underlying bitcoind processes. |
| `setup_clean_chain` | `False` | A 200-block-long chain is initialized from cache by default. Instead, `setup_clean_chain` initializes an empty blockchain if set to `True`. |
| `randomseed` | Random Integer | `TestShell().options.randomseed` is a member of `TestShell` which can be accessed during a test to seed a random generator. User can override default with a constant value for reproducible test runs. |
| `supports_cli` | `False` | Whether the bitcoin-cli utility is compiled and available for the test. |
| `tmpdir` | `"/var/folders/.../"` | Sets directory for test logs. Will be deleted upon a successful test run unless `nocleanup` is set to `True` |
| `trace_rpc` | `False` | Logs all RPC calls if set to `True`. |
| `usecli` | `False` | Uses the bitcoin-cli interface for all bitcoind commands instead of directly calling the RPC server. Requires `supports_cli`. |
