Certainly! Below is the complete `Cargo.toml`, `src/lib.rs`, and instructions to build and test the code.

### Cargo.toml
```toml
[package]
name = "random_multiplier"
version = "0.1.0"
edition = "2021"

[dependencies]
rand = { version = "0.8", features = ["derive"] }  # Updated to a more recent version of rand with feature for derive macros
```

### src/lib.rs
```rust
use rand::Rng;  // Import the Random trait from rand crate

/// Generates a random number between 1 and 10 using rand::thread_rng() and multiplies it by `param`.
///
/// # Examples
///
/// ```
/// assert_eq!(random_multiplier::solution(2), 20); // Check if multiplication works with a simple case
/// assert_eq!(random_multiplier::solution(5), 50); // Another test case with different input
/// assert_eq!(random_multiplier::solution(1), 10); // Edge case where param is 1
/// ```
pub fn solution(param: i32) -> i32 {
    let random_number = rand::thread_rng().gen_range(1..=10);

    random_number * param
}

// Test function for solution to ensure it returns the correct result
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_solution() {
        assert_eq!(solution(2), 20); // Check if multiplication works with a simple case
        assert_eq!(solution(5), 50); // Another test case with different input
        assert_eq!(solution(1), 10); // Edge case where param is 1
    }
}
```

### Build and Test

To build the code with tests, run:
```bash
cargo build --tests
```

This will compile the code and run all the tests.

To run the tests individually, you can use:
```bash
cargo test <test_name>
```

For example, to run only the `test_solution` test, you would use:
```bash
cargo test test_solution
```

### Final Summary

- **Cargo.toml**:
  ```toml
  [package]
  name = "random_multiplier"
  version = "0.1.0"
  edition = "2021"

  [dependencies]
  rand = { version = "0.8", features = ["derive"] }  # Updated to a more recent version of rand with feature for derive macros
  ```

- **src/lib.rs**:
  ```rust
  use rand::Rng;  // Import the Random trait from rand crate

  /// Generates a random number between 1 and 10 using rand::thread_rng() and multiplies it by `param`.
  ///
  /// # Examples
  ///
  /// ```
  /// assert_eq!(random_multiplier::solution(2), 20); // Check if multiplication works with a simple case
  /// assert_eq!(random_multiplier::solution(5), 50); // Another test case with different input
  /// assert_eq!(random_multiplier::solution(1), 10); // Edge case where param is 1
  /// ```
  pub fn solution(param: i32) -> i32 {
      let random_number = rand::thread_rng().gen_range(1..=10);

      random_number * param
  }

  // Test function for solution to ensure it returns the correct result
  #[cfg(test)]
  mod tests {
      use super::*;

      #[test]
      fn test_solution() {
          assert_eq!(solution(2), 20); // Check if multiplication works with a simple case
          assert_eq!(solution(5), 50); // Another test case with different input
          assert_eq!(solution(1), 10); // Edge case where param is 1
      }
  }
  ```

- **Build**:
  ```bash
  cargo build --tests
  ```

- **Test**:
  ```bash
  cargo test <test_name>
  ```