Table Testing Go Generics

I'm excited for Go 1.18 and wanted to test the new generics feature. Feels pretty neat to use, but I stumbled over an issue:

How do you table test generic functions?

I came up with this code, but I need to redeclare my testing logic over each function since I can't instantiate T values. (Inside my project I use structs instead of string and int. Just didn't want to include them because it's already enough code)

How would you approach this problem?

Edit: Here's the code:

package main

import (
    "testing"

    "github.com/stretchr/testify/assert"
)

type Item interface {
    int | string
}

type store[T Item] map[int64]T

// add adds an Item to the map if the id of the Item isn't present already
func (s store[T]) add(key int64, val T) {
    _, exists := s[key]
    if exists {
        return
    }
    s[key] = val
}

func TestStore(t *testing.T) {
    t.Run("ints", testInt)
    t.Run("strings", testString)
}

type testCase[T Item] struct {
    name     string
    start    store[T]
    key      int64
    val      T
    expected store[T]
}

func testString(t *testing.T) {
    t.Parallel()
    tests := []testCase[string]{
        {
            name:  "empty map",
            start: store[string]{},
            key:   123,
            val:   "test",
            expected: store[string]{
                123: "test",
            },
        },
        {
            name: "existing key",
            start: store[string]{
                123: "test",
            },
            key: 123,
            val: "newVal",
            expected: store[string]{
                123: "test",
            },
        },
    }
    for _, tc := range tests {
        t.Run(tc.name, runTestCase(tc))
    }
}

func testInt(t *testing.T) {
    t.Parallel()
    tests := []testCase[int]{
        {
            name:  "empty map",
            start: store[int]{},
            key:   123,
            val:   456,
            expected: store[int]{
                123: 456,
            },
        },
        {
            name: "existing key",
            start: store[int]{
                123: 456,
            },
            key: 123,
            val: 999,
            expected: store[int]{
                123: 456,
            },
        },
    }
    for _, tc := range tests {
        t.Run(tc.name, runTestCase(tc))
    }
}

func runTestCase[T Item](tc testCase[T]) func(t *testing.T) {
    return func(t *testing.T) {
        tc.start.add(tc.key, tc.val)
        assert.Equal(t, tc.start, tc.expected)
    }
}

from Recent Questions - Stack Overflow https://ift.tt/eZrpvK6
https://ift.tt/9Nrius1