Simple Student Query Engine

Built to solve:

Given a list of test results (each with a test date, Student ID, and the student's Score)
from an external data source, return the Final Score for each student for a user-provided
date range. A student's Final Score is calculated as the average of his/her 5 highest test
scores. You can assume each student has at least 5 test scores.

Notes:

• For an example implementation, I decided the "external data source" would be a file.
  • Obviously this could easily be a REST/SOAP API, DB, binary dump, etc...
• I also chose a cmd-line interface over a REST or similar.
• For a throwaway code project like this, I focused on code-readability, and not optimization.

Usage: main.rb [options]
    -f, --file FILE                  File containing student data, e.g. sampledata.txt
    -i, --id STUDENT                 Student ID (optional to filter output)
    -s, --start [TIME]               Start Timestamp for student test results, e.g. 1409258913
    -e, --end [TIME]                 End Timestamp for student test results, e.g. 1409258913

Example output:

> ruby main.rb -s 1 -e 2409258915
Defaulting file input to 'sampledata.txt'!
Student 0001: 90%
Student 0002: 86%

Code Layout:

• student_datasource.rb - holds the main interface for accessing data loaded from an external source.
• student_score.rb - contains the class definition for the record representing an instance of a test result.
• score_calculator.rb - holds the algorithm for determining the final score.
• file_data_source.rb - An example implementation of an external source reader.
• tests/calculator_test.rb - unit tests for the final score calculator.
• tests/file_loader_test.rb - unit tests for the loading of student data from file.
• tests/student_db_test - unit and functional tests for the main interface for external data sources.

Running the code:

• Run the following commands from the root directory of wherever you put these files.
• To run based on sample data located in 'sampledata.txt': 'ruby main.rb -s 1 -e 2409258915'
• To run the test suite: 'rake test'

Interview Requirements

• Works?

  • You should be able to test that it works by providing a text file with sample data and then querying the program via the command line.
  • E.g., 'ruby main.rb -f sampledata.txt -i 0002 -s 1 -e 1509258914'

• Tested?

  • A series of small unit and functional tests exercise the code.
  • Run them with 'rake test'.

• Well designed?

  • Designed using the strategy pattern to allow external sources to be swapped out, e.g. REST API instead of the File loader. Instead of instantiating a FileDataSource object to pass to our StudentDB interface, maybe instantiate a SqlDataSource object.
  • Assumption was that there was a max number of students that would fit into memory.
  • Number of highest grades to average is mutable by just specifying an optional parameter to our ScoreCalculator object.
  • Score dates are stored as timestamps which simplifies a lot of things, and if needed can be converted back to human-readable for display purposes.

• Code readability?

  • Code is short thanks to Ruby's duck and dynamic typing.

• Extendible and maintainable?

  • Should be able to swap out various external sources easily without modifying core code.
  • Code was written to be readable rather than optimized.
  • Should be no problem to put different interfaces on top of this code, e.g. REST interface.
  • Number of highest grades is not hardcoded, but does default to 5.