# `GEPA.LLM.Mock`
[🔗](https://github.com/nshkrdotcom/gepa_ex/blob/v0.3.0/lib/gepa/llm/mock.ex#L1)

Mock LLM implementation for testing.

Returns deterministic responses for testing the optimization loop without
making actual API calls. Useful for:
- Unit testing
- Integration testing
- CI/CD pipelines
- Development without API keys

## Examples

    # With fixed responses
    llm = GEPA.LLM.Mock.new(responses: ["Response 1", "Response 2"])
    {:ok, "Response 1"} = GEPA.LLM.complete(llm, "Any prompt")
    {:ok, "Response 2"} = GEPA.LLM.complete(llm, "Any prompt")

    # With dynamic response function
    llm = GEPA.LLM.Mock.new(response_fn: fn p -> "Echo: " <> p end)
    {:ok, "Echo: Hello"} = GEPA.LLM.complete(llm, "Hello")

    # Default behavior (improved instructions)
    llm = GEPA.LLM.Mock.new()
    {:ok, response} = GEPA.LLM.complete(llm, "test prompt")

# `t`

```elixir
@type t() :: %GEPA.LLM.Mock{
  call_count: non_neg_integer(),
  response_fn: (GEPA.LLM.prompt() -&gt; String.t()) | nil,
  responses: [String.t()] | nil
}
```

# `complete`

```elixir
@spec complete([map()]) :: {:ok, %{content: String.t()}}
```

Legacy complete function for backward compatibility.

Prefer using `GEPA.LLM.complete/3` instead.

# `generate`

```elixir
@spec generate(String.t()) :: {:ok, String.t()}
```

Legacy generate function for backward compatibility.

Prefer using `GEPA.LLM.complete/3` instead.

# `new`

```elixir
@spec new(keyword()) :: t()
```

Creates a new Mock LLM instance.

## Options

  - `:responses` - List of fixed responses to cycle through
  - `:response_fn` - Function to generate dynamic responses (prompt -> response)
  - If neither is provided, uses default improvement behavior

## Examples

    # Fixed responses
    llm = GEPA.LLM.Mock.new(responses: ["Yes", "No", "Maybe"])

    # Dynamic responses
    llm = GEPA.LLM.Mock.new(response_fn: fn p -> "Processed: " <> String.upcase(p) end)

    # Default behavior
    llm = GEPA.LLM.Mock.new()

---

*Consult [api-reference.md](api-reference.md) for complete listing*