Angular Pipe Testing Challenge: Currency Formatting

This challenge focuses on writing unit tests for a custom Angular pipe that formats numbers as currency. Testing pipes is crucial for ensuring consistent and predictable data presentation within your Angular applications, especially when dealing with financial or monetary values. Successfully completing this challenge will demonstrate your understanding of Angular pipes and their testing methodologies.

Problem Description

You are tasked with creating and testing a custom Angular pipe named CurrencyPipeCustom that formats a number as currency according to a specified locale. The pipe should accept a number and a locale code (e.g., 'en-US', 'fr-CA') as input and return a string representing the number formatted as currency for that locale. The pipe should handle both positive and negative numbers correctly. You need to write unit tests using Jasmine and Angular's testing utilities to verify the pipe's behavior with various inputs and locales.

Key Requirements:

• Create the Pipe: Implement the CurrencyPipeCustom pipe.
• Locale Support: The pipe must correctly format numbers based on the provided locale.
• Positive and Negative Numbers: The pipe must handle both positive and negative numbers accurately.
• Unit Tests: Write comprehensive unit tests to cover various scenarios, including different locales, positive numbers, negative numbers, and potentially zero.
• Error Handling (Optional): Consider how the pipe should behave if an invalid locale is provided. While not strictly required for the core functionality, a robust solution might include some basic error handling or default behavior.

Expected Behavior:

• When given a number and a valid locale, the pipe should return a string representing the number formatted as currency for that locale.
• The formatting should adhere to the conventions of the specified locale (e.g., currency symbol placement, decimal separator, grouping separator).
• Negative numbers should be displayed with a negative sign.
• Invalid locales should either result in a default formatting or an error (depending on your implementation choice).

Edge Cases to Consider:

• Zero values.
• Large numbers.
• Numbers with many decimal places.
• Invalid or unsupported locales.
• Non-numeric input (though the pipe is expected to receive a number, consider how it might handle unexpected input).

Examples

Example 1:

Input: 1234.56, 'en-US'
Output: $1,234.56
Explanation: The number 1234.56 is formatted as US currency, including the dollar sign and comma as a thousands separator.

Example 2:

Input: -50.00, 'fr-CA'
Output: -50,00 $
Explanation: The number -50.00 is formatted as Canadian French currency, including the currency symbol after the amount and a comma as a decimal separator.

Example 3:

Input: 0, 'de-DE'
Output: 0,00 €
Explanation: Zero is formatted as German currency, including the euro symbol and two decimal places.

Constraints

• The pipe must be written in TypeScript.
• Tests must be written using Jasmine and Angular's testing utilities.
• The solution should be well-structured and easy to understand.
• Performance is not a primary concern for this challenge, but avoid unnecessarily complex or inefficient code.
• The pipe should be a pure function (i.e., it should not have any side effects).

Notes

• Angular provides a built-in CurrencyPipe. This challenge is about creating and testing your own custom pipe.
• Consider using TestBed to create a testing module that includes your pipe.
• Use expect assertions to verify the output of the pipe.
• Think about how to mock or stub any dependencies your pipe might have (though this is unlikely for a simple currency formatting pipe).
• Focus on writing clear, concise, and well-documented tests. Good test coverage is more important than the absolute minimum number of tests.