extern crate in doctest

Cargo.lock

[root]
name = "playground"
version = "0.1.0"
dependencies = [
 "serde_json 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
]

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name = "itoa"
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source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "num-traits"
version = "0.1.37"
source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "serde"
version = "1.0.2"
source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "serde_json"
version = "1.0.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
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 "num-traits 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
]

[metadata]
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"checksum itoa 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "eb2f404fbc66fd9aac13e998248505e7ecb2ad8e44ab6388684c5fb11c6c251c"
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Cargo.toml

[package]
authors = ["Pascal Hertleif <killercup@gmail.com>"]
name = "playground"
version = "0.1.0"

[lib]
path = "lib.rs"

[dependencies]
serde_json = "1.0.1"

lib.rs

/// Return a random integer
///
/// ```rust
/// # #[macro_use] extern crate serde_json as json;
/// # extern crate playground;
/// # use playground::*;
/// # fn main() {
/// let value = random_int();
/// let response = json!({"val": value});
/// assert!(response["val"].is_i64());
/// # }
/// ```
pub fn random_int() -> i32 {
    4
}

fn main() {}