Captures stdout output from a function and parses it as JSON.

This is useful for testing code that outputs JSON to stdout, such as CLI tools, hooks, or any code that communicates via structured output rather than return values.

Options

• :stderr - When true, also captures stderr output during function execution.

          This is useful when the function being tested may output to stderr
          (e.g., compilation warnings) that would otherwise interfere with
          JSON parsing. Default: `false`

Examples

json = Claude.Test.capture_json_stdout(fn ->
  MyModule.process(input)
end)

assert json["status"] == "success"
assert json["data"]["count"] == 42

# Capture stderr as well to avoid interference
json = Claude.Test.capture_json_stdout(fn ->
  MyModule.compile_and_run(input)
end, stderr: true)

Raises

Raises an error if the captured output is not valid JSON.

Returns

Returns the parsed JSON as an Elixir map.

Creates a file with the given content in the specified directory.

Returns the full path to the created file.

Examples

# Create a simple Elixir module
path = Claude.Test.create_file(test_dir, "lib/example.ex", """
defmodule Example do
  def hello, do: :world
end
""")

# Create a config file
Claude.Test.create_file(test_dir, "config/config.exs", """
import Config
config :my_app, key: :value
""")

Arguments

• base_dir - The base directory where the file should be created
• relative_path - The relative path from the base directory
• content - The content to write to the file

The function will create any necessary parent directories.

Runs a hook with the given input and returns the parsed JSON output.

This helper automatically:

• Encodes the input struct to JSON (if not already a string)
• Calls the hook's run/1 function
• Captures the stdout output
• Parses the output as JSON

Options

• :stderr - When true, also captures stderr output during hook execution.

          This is useful when the hook may output to stderr (e.g., compilation
          warnings) that would otherwise interfere with JSON parsing.
          Default: `false`

Examples

# With a fixture struct
input = Fixtures.pre_tool_use_input(tool_name: "Edit")
json = Claude.Test.run_hook(MyHook, input)
assert json["decision"] == "allow"

# With already-encoded JSON
json_string = ~s({"tool_name": "Write"})
json = Claude.Test.run_hook(MyHook, json_string)

# Inline with fixtures
json = Claude.Test.run_hook(MyHook, Fixtures.post_tool_use_input())
assert json["suppressOutput"] == true

# Capture stderr during hook execution
json = Claude.Test.run_hook(MyHook, input, stderr: true)
assert json["decision"] == "block"

Arguments

• hook_module - The hook module with a run/1 function
• input - Either a struct that can be JSON encoded, or a JSON string
• opts - Keyword list of options (optional)

Returns

The parsed JSON output from the hook as an Elixir map.