测试从数据库查询的结果集中返回唯一值的方法

Question

Let's say there is a database table named "Students".

         Students Table
|---------------|---------------|
|     Name      |      Age      |
|---------------|---------------|
|     John      |       9       |
|---------------|---------------|
|     Jane      |       7       |
|---------------|---------------|
|     Dana      |       8       |
|---------------|---------------|
|     John      |       6       |
|---------------|---------------|

I make a request to the database to return all names using:

SELECT Name FROM Students

So the result set would be:

ResultSet rs = {"John" "Jane" "Dana" "John"}

I then want to return all unique values so I write a method called populateSet() to populate a HashSet setOfNames with rs .

After executing populateSet(ResultSet rs) , only unique names appear:

"John" "Jane" "Dana"

Here is the validation test:

public void testValidation() {
    // Skipping the test data / db connection / query part
    ResultSet rs = ResultSet received back from DB
    Set<String> expected = {"John", "Jane", "Dana"};
    Set<String> actual = WhateverClass.populateSet(rs);
    assertEquals(expected, actual);
}

What are some of the possible unit tests that I could write?

I know I should write a null, empty, and negative tests. What are some corner cases?

Answer 1

Potential corner cases:

• Very large table (millions of rows)
• Transactionality - eg, what happens if a name is inserted/deleted/updated after you start the table scan?
• Data ordering
• Case sensitivity/insensitivity of names
• non-ASCII characters in names