PermissionSetAssignmentController.cls

public with sharing class PermissionSetAssignmentController {
    
    public List<PermissionSetAssignment> permissionSetAssignments {get; set;}
    
    public PermissionSetAssignmentController() {
        this.permissionSetAssignments = [
            SELECT
                  Id
                 ,AssigneeId
                 ,Assignee.Name
                 ,PermissionSetId
                 ,PermissionSet.Name
            FROM
                PermissionSetAssignment
            ORDER BY Id ASC
            LIMIT 1000
        ];
    }
}

PermissionSetAssignmentControllerTest.cls

@isTest
private class PermissionSetAssignmentControllerTest {

    static testMethod void PermissionSetAssignmentControllerTest() {
        Test.startTest();
        
        PermissionSetAssignmentController cls = new PermissionSetAssignmentController();
        System.assertEquals(cls.permissionSetAssignments.isEmpty(), false);
        
        Test.stopTest();
    }
}

PermissionSetAssignmentView.page

<apex:page controller="PermissionSetAssignmentController" showHeader="true" sidebar="false">
    <div id="vf-page">
        <apex:form id="form">
            <apex:pageBlock title="{!$ObjectType.PermissionSetAssignment.Label}" id="block">
                <apex:pageBlockTable value="{!permissionSetAssignments}" var="item">
                    <apex:column headerValue="{!$ObjectType.PermissionSetAssignment.Fields.Id.Label}">
                        <apex:outputText value="{!item.Id}" />
                    </apex:column>
                    <apex:column headerValue="{!$ObjectType.PermissionSetAssignment.Fields.AssigneeId.Label}">
                        <apex:outputText value="{!item.AssigneeId}" />
                        <br/>
                        <apex:outputText value="{!item.Assignee.Name}" />
                    </apex:column>
                    <apex:column headerValue="{!$ObjectType.PermissionSetAssignment.Fields.PermissionSetId.Label}">
                        <apex:outputText value="{!item.PermissionSetId}" />
                        <br/>
                        <apex:outputText value="{!item.PermissionSet.Name}" />
                    </apex:column>
                </apex:pageBlockTable>
            </apex:pageBlock>
        </apex:form>
    </div>
</apex:page>